[DavidKok]

I've been looking at the details of the Dutch Doubleton system I'm familiar with. This post contains some of my thoughts and ideas, but is more of a stream of consciousness than a well thought out post. My goal is to give a bit more insight in Dutch Doubleton while at the same time identifying its weaknesses, and exploring some ideas for moving the system more towards a Polish Club.

In the last few weeks I've managed to get Henk Uijterwaal's 'dealer' software running on my PC, and I've started crunching numbers on a wide variety of topics (ranging from 'how often do we open the bidding' through 'what is third hand's HCP distribution if partner opens and we get overcalled' to 'what is the chance of landing in an 8+ card fit with an assumed fit preempt'). One big caveat is that it was too much work to attempt to fully emulate judgement in the bidding, so I simplified in the hopes of creating about an equal share of false positives and false negatives, keeping the total percentages reasonable (for example, instead of my normally aggressive weak two's I demanded that we have at least a 5-card suit (but we don't nearly open most 5-card suits with a weak two), no undisclosed 4cM (which we might sometimes have) and at least half our points in the long suit (which is also not always accurate) with 5-10 HCP and no rule of 20 opening).

A few sequences of Dutch Doubleton stood out as likely losers - allocating lots of valuable bidding space to infrequent hand types, which sometimes had completely fine alternative sequences as well. For example, consider the approximate opening percentages of each bid through 2NT in the spoiler¹:

Spoiler

pass: natural (~51.3%)
1♣: 12-13 bal no 5cM (~5.9%), 17-19 bal no 5cM (~2.1%), 11-23 semibal or unbal with 5(+) clubs or (4441) no club shortage (~5.9%) (total: ~13.8%)
1♦: semibal or unbal 5(+) diamonds or 4=4=4=1, 11-23 (~5.6%)
1♥: 11-21 5(+) hearts, can be balanced (~7.3%)
1♠: 11-21 5(+) spades, can be balanced (~7.6%)
1NT: 14-16 balanced (not semibalanced) no 5cM (~5.4%)
2♣: 22-23 balanced or semibalanced, 22-23 with a long major, 24+ any (~0.3%)
2♦: 5(+) card weak two, no 4cM (~2.3%)
2♥: 5(+) card weak two, no 4c♠ (~3.0%)
2♠: 5(+) card weak two, no 4c♥ (~3.0%)
2NT: 20-21 balanced or semibalanced (~0.6%)

¹More accurately, these are the probabilities of being dealt a hand that meets the criteria of the corresponding call. At the table it is very likely someone else will open the bidding when you're not in first seat.

Among other things the 2♣ opening stands out as a sore loser. This bid is a necessary evil in natural systems, but reserving such a relatively cheap opening bid for a ~1/300 hand type conditional on nobody preempting us seems lousy. It is somewhat popular to include a weak option in this bid (usually a weak two in diamonds, reserving 2♦ for the multi, or alternatively a weak opening with at least 5-4 in the majors) but I don't like those options at all. They make it very risky to competitively/preemptively raise partner, and the 'both majors' version in particular forces opener to jump to 3M on 2♣-2♦* (pick your longest major if weak); ? with a strong unbalanced hand. They also give the opponents multiple bites at the apple when weak, which it almost always is.

So instead I've been browsing the system notes of Polish club players (Dan Neill's website helpfully has many system overviews). Some of these Polish club systems closely resemble Dutch Doubleton, giving me hope that there might be a hybrid system where I get to use my experience with Dutch Doubleton, but fold that nasty 2♣ opener into the 1♣ opening. The basic structure over 1♣ is:
1♦ - any weak hand (approx 0-5, 0-6 or 0-7 HCP depending on flavour), or a hand of any strength with natural diamonds, or a balanced hand with some values, support for clubs but no desire to hog the hand (e.g. 3=3=3=4 or 3=2=3=5). Optionally also some hands with both majors (in Dutch Doubleton), but this is infrequent and can be confusing.
1♥ - natural (4+), shows some strength (6+, 7+ or 8+, again depending on flavour), may contain a long minor (Walsh-style) if not GF.
1♠ - natural (4+), shows some strength (6+, 7+ or 8+, again depending on flavour), may contain a long minor (Walsh-style) if not GF.
Over 1♣*-1M opener rebids naturally (and is assured of some values opposite). Over 1♣*-1♦* opener rebids naturally but folds the 12-13 balanced hands into a 1M reply (in DD: always 1♥. In older DD systems as well as some of the Polish club systems: bid your longer major, 3+), so that 1♣*-1♦*; 1NT shows 17-19 NF.
The main differences compared to my Dutch Doubleton that stand out to me are:

• A 2♣ opening shows ~10-15, 6(+) clubs. Some pairs also include 4♦5♣ too weak to reverse. I think 4M6♣ is allowed always while 4M5♣ is not, or maybe there are just different ways to show this hand type and it is up to judgement/preference. The pairs who insist on 6(+) clubs seem to open 1♦ with 4♦5♣ and too weak to reverse (or you can treat the hand as balanced, if appropriate).
  
• This frees 1♣-1X; 2♣ to show 16+ not balanced, long clubs, artificial (and usually forcing) and includes all natural reverses with long clubs.
  
• This frees 1♣-1X; 2♦ as an artificial relay, conveying something along the lines of 'hey partner, I had a standard 2♣ opening'. It also frees up 1♣-1♦; 2M, 1♣-1♥; 2♠ and 1♣-1♠; 2♥.

Several Polish systems open 1♣ with any (say) 18+ hand, so that you don't need tools like Gazzilli over 1M openings, and can reap the benefits of (somewhat) limited openers. My goals are less ambitious: I just want to fold most 22+ hands in there. So far I've tried something simple (opponents silent):

• On the auction 1♣*-1♦*; ?, use the jumps to 2♥ and up identical to the standard auction 2♣-2♦; ?.
  
• On the auction 1♣*-1♥; ?, use 2♦* as an artificial relay forcing 2♥, and opener's next bid is identical to that of the standard auction 2♣-2♦; ?. Use 1♣*-1♥; 2♠* as an artifical GF relay establishing hearts as trumps. This loses all sequences starting 2♣-2♦; 2♥, but almost all of those contain natural hearts (I play Kokish here) so they fold into the 2♠ bid nicely. The only hand types that are now hard to show are the balanced hands that go through Kokish normally.
  
• On the auction 1♣*-1♠; ? use 2♦* as an artificial relay forcing 2♥, and opener's next bid is identical to that of the standard auction 2♣-2♦; ? (not 2♥). The auction 1♣*-1♠; 2♥* is the Kokish relay, and shows that opener has a hand that would have bid 2♣-2♦; 2♥ in standard.

I think this is relatively simple (keep your current 2♣ structure but open 1♣ instead) and has the benefit of describing responder's hand somewhat before we enter the strong artificial auctions. The Precision-esque 2♣ opening also seems like a winner, although I am a bit disappointed that I can't use the bid for some preemptive hand instead (so rather than opening more hand types this would open the same ones with greater accuracy). The Kokish-balanced hands over 1♣-1♥ are also an issue, albeit an infrequent one (the 1M responses to 1♣ show 8+ in Dutch Doubleton, so we're looking at at least 24HCP balanced opposite 8HCP with exactly hearts here).

I'm currently still looking for good rebid systems over 1♣*-1♦*; 2♣* and 1♣*-1M; 2♣* to untangle the reverses, keeping in mind these 2♣* rebids can be very wide ranging (from a minimum reverse to a decent 22-count), a good system over the natural 2♣ opening (most Precision systems have one, I'd welcome any and all recommendations) or general suggestions for changing up the approach. I currently also don't assign any meaning to the auction 1♣*-1♦*; 2♦. There is also a serious issue of interference over 1♣*, although I've tried to minimise that by not including a whole host of ~18-21 HCP hands regardless of shape.

Lastly it is interesting to note that modern Dutch Doubleton systems (as well as several natural systems) have already started using a version of this artificial 2♦ relay, using:

• 1♣*-1M; 2♦*-2♥ (forced); 2NT shows 17-19 balanced (GF, since partner shows 8+).
  
• 1♣*-1M; 2♦*-2♥ (forced); 2♠/3X shows a club-diamond reverse with a feature (optionally the 3♣ bid doesn't say anything about diamonds, a classical 'fake reverse', and just shows a GF hand with long clubs and no support for partner's major).
  
• 1♣*-1M; 2♦*-2♥; 2/3M (responder's suit) shows an artificial GF 4-card raise, allowing for better slam investigation.
  
• 1♣*-1M; 2NT shows the 'Bridge World Death Hand' with approximately 16+ HCP, a good long (6+) club suit and exactly 3-card support for partner.

My approach above attempts to make better use of this relay by (loosely) copying Polish club methods.

[helene_t]

Team Oranje once (some 15 years ago) introduced the "Oranje Klaveren" which everyone in the team was supposed to play, I think Jasma-Verhees played it for a while and now only Jansma/Jansma play it I think. It is very similar to Polish club and that what was stroke me also at first when I saw your post - why not just play WJ instead of reinventing the wheel?

But now I realize that you allow 1♦ and 1M openings with up to 21 or so, so the load on the 1♣ opening is less severe than in WJ. Also, the 1♣ opening includes 12-14 bal in WJ, 12-13 in your system, which presumably means that responder doesn't invite opposite the weak option which is nice.

I am not sure if I would like to play the 1M openings as (virtually) unlimited, I sorta like the 11-17 range in WJ, but I am sold on the wide ranging 1♦ opening.

Another difference with WJ is that you open 1♣ with (43)15, (41)35 and 4405 and 11-15 points which would open 2♣ in WJ. I like that, especially given that you have taken some strain on the 1♣ opening elsewhere. Note that in WJ, you open 1♣ with 4414 any strength anyway so you have to cater to the 3-suited hands anyway and then you may as well consider (43)15 three-suited to keep the 2♣ opening clean. Of course you can take some liberties with the 2♣ opening in 3rd/4th, depending on suit quality and vulnerability.

But with (41)35 I think I would prefer to open 1♦, the load on the 1♦ opening is quite low and if you play negative freebids as in WJ it is nice not to have a singleton in the suit which partner bids non-forcingly at the 2-level.

As for responses to the 2♣ opening, what about switching the 2♥/♠ responses, then you can get the best of two worlds when responder has spades (with natural 2M responses you have the dilemma if 2M is forcing or not).

[dokoko]

Looking at it from the other side of your path it seems you want to modify Polish Club by removing several strong hands out of the 1♣ opening thereby making other 1-level openings less well-defined.

IMO this will not improve over Polish Club.

[DavidKok]

helene_t, on 2022-December-30, 16:46, said:

Team Oranje once (some 15 years ago) introduced the "Oranje Klaveren" which everyone in the team was supposed to play, I think Jasma-Verhees played it for a while and now only Jansma/Jansma play it I think. It is very similar to Polish club and that what was stroke me also at first when I saw your post - why not just play WJ instead of reinventing the wheel?

But now I realize that you allow 1♦ and 1M openings with up to 21 or so, so the load on the 1♣ opening is less severe than in WJ. Also, the 1♣ opening includes 12-14 bal in WJ, 12-13 in your system, which presumably means that responder doesn't invite opposite the weak option which is nice.

Thank you for the suggestion, I'll look into this! The 14-16NT opening has been a clean winner in Dutch Doubleton, and opening balanced 11's got us in hot water (costing about as often as it gained), so we kept the 12-13 weak range. It seems to work fine, that's the only reason I have these specific ranges.

helene_t, on 2022-December-30, 16:46, said:

I am not sure if I would like to play the 1M openings as (virtually) unlimited, I sorta like the 11-17 range in WJ, but I am sold on the wide ranging 1♦ opening.

I've never regretted opening 1M with an 18+ count. If the opponents don't interfere we have Gazzilli for descriptive auctions over 1NT, and over 2♣ and higher we're in a great spot. Plus it protects against preemption, especially with shortage in the other major. I haven't compared this with 18+ Polish club openings, I just didn't feel a particular need to take them out. As far as I can tell most Polish Club systems don't play Gazzilli or the likes (there doesn't seem to be a need), but I don't think that's a weak part of our system to begin with.

helene_t, on 2022-December-30, 16:46, said:

Another difference with WJ is that you open 1♣ with (43)15, (41)35 and 4405 and 11-15 points which would open 2♣ in WJ. I like that, especially given that you have taken some strain on the 1♣ opening elsewhere. Note that in WJ, you open 1♣ with 4414 any strength anyway so you have to cater to the 3-suited hands anyway and then you may as well consider (43)15 three-suited to keep the 2♣ opening clean. Of course you can take some liberties with the 2♣ opening in 3rd/4th, depending on suit quality and vulnerability.

But with (41)35 I think I would prefer to open 1♦, the load on the 1♦ opening is quite low and if you play negative freebids as in WJ it is nice not to have a singleton in the suit which partner bids non-forcingly at the 2-level.

I'm not a fan of negative freebids, especially not if opener can be wide ranging. I'd much rather play transfer responses in competition, as an example.
I've had some more time to think about it, and I think exactly 1=4=3=5 hands are awkwardly placed on 1♣-1♠, and will have to rebid 1NT (or have opened 1NT). I'm not sure how I feel about this, it certainly isn't an upside.
Being able to raise an unbalanced diamond in competition with a 3-card suit is really comfortable, and I don't foresee rebid problems after 1♣ with 4=1=3=5 weak (just rebid spades).

helene_t, on 2022-December-30, 16:46, said:

As for responses to the 2♣ opening, what about switching the 2♥/♠ responses, then you can get the best of two worlds when responder has spades (with natural 2M responses you have the dilemma if 2M is forcing or not).

Thank you, this sounds interesting!

dokoko, on 2022-December-30, 17:37, said:

Looking at it from the other side of your path it seems you want to modify Polish Club by removing several strong hands out of the 1♣ opening thereby making other 1-level openings less well-defined.

IMO this will not improve over Polish Club.

Thank you, the goal wasn't to improve over Polish Club openings, but to apply Dutch Doubleton answers to a system similar enough to Polish Club. I think the response structure of Dutch Doubleton is amazingly sound. I'm not quite prepared to learn an entirely new system, I just wanted to eliminate the strong 2♣ opening.

[DavidKok]

Is the range of 18+ for Polish Club determined by the fact that positive 1M responses show ~6HCP or so, so that 18-opposite-6 can freely force to game, e.g. on the Polish Club auction 1♣*-1♠; 2♥* (18+ with 5(+) hearts, does not say anything about clubs)? If so, do you not lose definition compared to the 'standard' 2♣*-2♦*; 2♥ (approximately 22+ with hearts, although some may prefer to play Kokish)? You are assured of some values opposite, but it seems you might need a good structure to limit opener's hand on subsequent rounds of the bidding.

I've lost some of the excitement when I realised that all hands pattern out at the same level, if not higher, than they would in Dutch Doubleton. I still need to bid to 2M (or higher) before I can show the very big hands, my natural reverses don't gain definition, my ranges haven't gotten tighter and I don't get to open more hands. All this just for the 2♣ opener, which I'm not even sure is a big winner even if it shows 6(+) always. Come to think of it, isn't this also the case for a full Polish Club system? Which hand types are shown more accurately and/or at a lower level in Polish Club compared to Dutch Doubleton? Maybe there is room to win on exactly the auction 1♣*-1♦*; 2♦*. After all, responder will usually be (very) weak when we hold the ~23+ monster hand, and this saves a step compared to standard (we now have 2♦, 2♥ and 2♠ rebids for opener).

How difficult (or crazy) is it to try to eliminate the Polish 2♣ opening, assign that hand type (along with 'standard' unbalanced too-weak-to-reverse clubs hands) to 1♣-1X; 2♣ and fold the natural reverses into the very strong structure (GF opposite a Dutch Doubleton positive 1M response of 8+, so we have some room below the safety level)? We already play Lebensohl over natural reverses, presumably that structure is also suitable for unfolding responder's hand opposite a monster hand.

[nullve]

DavidKok, on 2022-December-30, 08:24, said:

Among other things the 2♣ opening stands out as a sore loser. This bid is a necessary evil in natural systems, but reserving such a relatively cheap opening bid for a ~1/300 hand type conditional on nobody preempting us seems lousy. It is somewhat popular to include a weak option in this bid (usually a weak two in diamonds, reserving 2♦ for the multi, or alternatively a weak opening with at least 5-4 in the majors) but I don't like those options at all. They make it very risky to competitively/preemptively raise partner, and the 'both majors' version in particular forces opener to jump to 3M on 2♣-2♦* (pick your longest major if weak); ? with a strong unbalanced hand. They also give the opponents multiple bites at the apple when weak, which it almost always is.

DavidKok, on 2022-December-31, 03:31, said:

I'm not quite prepared to learn an entirely new system, I just wanted to eliminate the strong 2♣ opening.

What I do in my (T-Walsh) system (and I'm sure much of the same can be done in Dutch Doubleton or Polish Club):

Relevant openings:

1♣ = "10+, NAT-ish or 11-13/17-19/23+ BAL" (so truly unlimited)
1♦ = "10+, NAT-ish or 20-22 BAL" (so truly unlimited)
1M = "10-21, 5+ M, unBAL"
1N = "14-16 BAL" (like in your system)
2♣: like (a version of) Multi 2♦ but with the only strong option being unBAL GF hands with primary hearts
2♦ = "canapé preempt anchored on spades OR unBAL GF with primary spades"

Note that Opener is well placed with a strong hand after both 2♣-3M(P/C) or 2♦-3♠(PRE).

Let me sketch how I'm able to play the 1m openings as truly unlimited.

I've mentioned many times that I play kind of switched 1M responses to 1♦ that allows a certain (PREpareD* and preparATORy**)*** 1♠ rebid

1♣-1♦; 1♠ = "4+ S or 10-15, 31(54)"
1♦-1♥; 1♠ = "4+ H or 10-15, 13(54)",

* It is prepared since I have to open 1♣ (not 1♦) with 10-15, 3154/4054/4153, and 1♦ (not 1♣) with 0445/1345/1435.
** It is preparatory since it's a way a longer suit can be shown later
*** PREDATOR is such a nice acronym that I'm tempted to use it although I'm not sure what the 1♠ rebid preys on

which in turn allows (among other things) the use of 2♣ over 1♦-1M as a second, stronger Gazzilli.

The Gazzillis

1♣-[1M-1]; 1N (NF!): includes most unBAL "16-18" (rule of 25 or better, < rule of 28) hands with < 3 M as well as 17-19 BAL with 2-3 M.
1♣-[1M-1]; 2♦: includes most unBAL "19-21" (rule of 28 or better, < rule of 31) hands
1♦-1OM; 1N (NF!): includes most unBAL "16-18" (rule of 25 or better, < rule of 28) hands as well as 20-22 BAL with 2-4(!) M
1♦-1OM; 2♣: includes most unBAL "19-21" (rule of 28 or better, < rule of 31) hands,

then makes it easy to reserve 1♣-1R; 2N+ and 1♦-1M; 2N+ for unBAL "22+" (rule of 31 or better) hands.

I also use something analogous to two Gazzillis both over 1♣-1♠/N and 1♦-1N but I won't go into any detail here.

[DavidKok]

Thank you. I am not a fan of preempts that don't show the suit they bid, the 'two bites at the apple' part is too much for me (and I have some excellent defences against most preempts in that class). I could include some balanced hands in the 1♦ opening, but prefer not to if at all possible. I've seen switch over 1♦ before and I think it's slightly better than standard but not a huge deal either way, unless I'm missing something vital. An unbalanced diamond gets to use 1NT as Gazzilli (16+ any or 6(+)♦ weak) over either major, though some people prefer transfer rebids instead (and I've also played that 1♦ contains (31)4♦5♣ 11-15, and shown that with a NF 1NT rebid over the short major, but I don't like it much).

I've been reading up on the Polish Club Odwrotka (artificial 1♣-1M; 2♦ sequence to untangle the strong hand types) and found an explanation of Bubrotka and Odwyrtka (modern variants) in the Wspólny Język 2005 document by Krzystof Jassem. I like a lot of those bidding sequences and think they can be used to help solve my particular requests. My current thoughts are:

• On 1♣*-1♦* (which contains all ~0-7 HCP hands that aren't some shapely weak jump) we are well placed. Currently the jump rebids for 2♥ and up are not in use in Dutch Doubleton and the 2♦ strong reverse is wasteful. It is almost child's play to just 'bid as if we had started 2♣-2♦', and this alone covers 76% of the auctions where we have a traditional strong 2 clubs opening (according to a little simulation). I might be able to do something clever with the 2♦ rebid here and gain on these sequences too, but if nothing else we can be near certain partner doesn't have 8HCP which is a benefit.
  
• On 1♣*-1M there is plenty of room for classical club-hearts and clubs-spades reverses. I would like to neatly shuffle traditional club-diamond reverses away somewhere, which would allow me to use 2♦ as 'I had a traditional 2♣ opener'. Since this would mean the partnership has at least 8+22HCP (or so) I don't mind making that bid forcing through 4♥ (so 3NT is forcing), which gives me more than enough bidding space to use, for example, Ingberman to have responder clarify their hand type. I've tried bidding a few dozen hands with just Ingberman and it all looked very reasonable (I bid a couple of grands, a couple of games, and a lot of small slams, some of which were unfortunately on a finesse - but pretty much all of these would have been hell to bid after a strong 2♣ opening!). For a first try without any gadgets I think that's very reasonable, but I'm looking to tinker around with it some more.
  
• One thing I did notice in the WJ system is that the NT ranges all get stretched a bit (the ladder is 12-14, 15-17, 18-20(21), 21-23(24) compared to the more standard 12-14, 15-17, 18-19, 20-21, 22+) as a consequence of not having enough strong balanced jump bids over the 1♣ opening. Balicki-Zmudzinski play(ed?) 12-14, 15-17, 18-21(!), 22+ if partner responds 1♦ and 12-14, 15-17, 18+ if partner shows a major, Greg Matula plays 12(+)-15(-), 15(+)-18(-), 18(+)-21(-), 22+ and I haven't had a chance to check more Polish club system notes yet. In a similar vein the bidding ladder for unbalanced hands with long clubs seems overloaded, to the point where decent 11-counts with 6C332 or 5C4M are systematically passed out to take pressure off of the 2♣ opening while guaranteeing that 1♣-1X; 2♣ shows at least traditional reverse strength.
  
• Dutch Doubleton plays 1♣-1X; 2♣ as wide ranging (say, 11-17) while a jump to 3♣ shows approximately 15-17 with concentrated values, and stronger hands start with a classical fake reverse. I think it makes sense to either
  • Try to keep this structure, fit ~17+ clubs hands or so into the artificial 2♦ rebid somehow (which would mean that bid shows 17+ with long clubs, a traditional clubs-diamond reverse, or 22+ artificial. A bit unwieldy, but the latter hand type can comfortable force to 4NT if needed).
    
  • Give up on 2♣ NF, and play it as wide-ranging forcing ('we lost the clubs years ago'). That lets me fold in the strong club hands and club-diamond reverses (I could even play around with the clubs-hearts reverses, the Polish Club includes these), and all it costs is stopping at a safe level on, say, 12 opposite 8 when the clubs play better than a major suit.

All in all I'm now again somewhat optimistic about this approach. The Odwrotka is a really good idea, focusing on letting responder clarify their hand type while containing almost exclusively natural followups in a strong forcing structure. The structure is so solid I'm not even convinced that the 3-card in support should be required - what are you supposed to bid with, say, a 21HCP 1=4=5=3 over 1♣-1♠? Why not ask for partner's strength and shape at a low level?


P.S.: I've read Oranje Klaveren system notes, I found two different versions (Jansma-Verhees and a different variant). The Jansma-Verhees system strongly resembles Dutch Doubleton, with a 2♣ opening showing a weak two in diamonds or a wide range of strong hand types. Some pressure has been lifted from this by moving 20+ (4441) hand types and 26+ balanced to 1♣-1♦; 2♦*-2♥*; ? (2♠ shows a natural club-diamonds reverse, 2NT shows 26+ balanced, 3X shows a 4441 with shortness in the suit above X with 3♠ showing club shortage) and GF hands with a long clubs suit to 1♣-1♦; 2NT/3♣. Over 1♣-1M; 2♦ they include a different response structure than the Odwrotka variants, and cite that it works well opposite 18-19 balanced and that clubs-diamond reverses 'should improvise a little' (and presumably the very strong hands just keep bidding). On the one hand that's bad news that I can't copy their structure, on the other hand if it's good enough for Jansma-Verhees I could just stop developing this here and call it good .
The second Oranje Klaveren version I found does include the Polish 2♣ opener, and it closely resembles the WJ system. As far as I can tell it seems like a summary of the WJ system, without any significant changes or upsides.

[awm]

In my opinion, there are a number of pretty serious problems with Polish Club systems, and I feel like I've generally done pretty well against people playing the system (in the bidding at least, the strongest Poles are certainly better card players). It will be interesting to see whether you can avoid some of these issues in your approach:

1. The Polish 1♣-1♦-1M auctions are really bad. The issue is that this rebid can be either a weak notrump with 3-4 in the major or something like 18-21 with a five card major. While this is nominally non-forcing, the latter hand type requires keeping the auction alive in a lot of places where it can be really dangerous opposite the former.
2. When opponents bid over the Polish 1♣, it can create a lot of problems. While it's true that people don't preempt like crazy the way they do over a strong club, the fact that you can't balance with 4234 after 1♣-(2♥)-Pass-(Pass) or even with a minimum 4414 after 1♣-(2♦)-Pass-(Pass) can be really costly.
3. Negative free bids and their repercussions lead to a number of problems in competitive sequences; the negative free bid itself can be problematic when opener is unbalanced, but more often it's the need to do something else with hands that would ordinarily make a forcing free bid, which can make finding the best game difficult. In my experience, Polish club players miss 5-3 major fits (responder having five) with some frequency, and also play 4M on a 4-3 fit more often than they should.
4. The Polish 2♣ opening isn't great -- in practice people seem to try an overly optimistic asking response because they really don't want to miss a 4-4 major fit, then get too high if that fit fails to materialise.

It does seem like you're addressing some of these so far!

[helene_t]

Adam: it seems that David has addressed issues 1 (strong hands with 5+ hearts rebid 2♥, not 1♥), issue 3 (transfer freebids) and issue 4 (2♣ shows 6+).

With respect to issue 2, I would think that opener can reopen with a minimum 4414, as the strong variants will be strong enough to take a 3rd bite at the apple.

David: The auction
1♣-1M
2NT
is GF in WJ as opener shows 18+, is that also the case in your system, or can 2NT be passed as opener could have just 17 points?

[DavidKok]

awm, on 2023-January-01, 08:59, said:

In my opinion, there are a number of pretty serious problems with Polish Club systems, and I feel like I've generally done pretty well against people playing the system (in the bidding at least, the strongest Poles are certainly better card players). It will be interesting to see whether you can avoid some of these issues in your approach:

1. The Polish 1♣-1♦-1M auctions are really bad. The issue is that this rebid can be either a weak notrump with 3-4 in the major or something like 18-21 with a five card major. While this is nominally non-forcing, the latter hand type requires keeping the auction alive in a lot of places where it can be really dangerous opposite the former.
2. When opponents bid over the Polish 1♣, it can create a lot of problems. While it's true that people don't preempt like crazy the way they do over a strong club, the fact that you can't balance with 4234 after 1♣-(2♥)-Pass-(Pass) or even with a minimum 4414 after 1♣-(2♦)-Pass-(Pass) can be really costly.
3. Negative free bids and their repercussions lead to a number of problems in competitive sequences; the negative free bid itself can be problematic when opener is unbalanced, but more often it's the need to do something else with hands that would ordinarily make a forcing free bid, which can make finding the best game difficult. In my experience, Polish club players miss 5-3 major fits (responder having five) with some frequency, and also play 4M on a 4-3 fit more often than they should.
4. The Polish 2♣ opening isn't great -- in practice people seem to try an overly optimistic asking response because they really don't want to miss a 4-4 major fit, then get too high if that fit fails to materialise.

It does seem like you're addressing some of these so far!

Thanks! To go in a bit more detail:

• I plan to play the full DD structure here, branching out the strong hands somewhere else. Of course this is work in progress, but right now I don't see singificant issues with 1♣-1♦; 1♥ as 1) 12-13 balanced, 2) hearts-clubs two-suiter (4(+)♥5(+)♣ or exactly 1=4=4=4/4=4=1=4), limited to below approx a strong 2♣ opener. DD 1♣-1♦; 1♠ shows 4(+)♠,5(+)♣ or exactly 4=1=4=4 and is limited to approximately 18, I intend to stretch this a bit to approximately 21 but keep the shape requirement. Over 1♣-1♦; 1♥ responder can ask for the hand type with 1♠ (which responder will do most of the time), with the DD answering scheme
  • 1NT: 12-13 balanced (neither confirms nor denies any particular major suit holding)
    
  • 2♣: 4(+)♥, 5(+)♣, 11-15(16).
    
  • 2♦: artificial and rare, we've had a few bidding accidents here but it shows 4=4=1=4/4=4=0=5 with 11-15.
    
  • 2♥: 4(+)♥, 5(+)♣, (16)17+ (sound reverse).
    
  • 2♠: 4=4=1=4/4=4=0=5 16+ (sound reverse, but that doesn't require all that many HCP with this shape).
• The very strong hands are very rare (~13.8% of all hands are a 'natural' DD 1♣ opener while only ~0.3% is very strong by my definition, a ratio of almost 50:1), so I doubt it will have a noticeable impact on our current structure after interference. It is also worth noting that approximately 2/3rds of those very strong hands are balanced, and trying to preempt against a 22-23 balanced hand tends to not work great. The 4=2=3=4 12-13 hand should pass on 1♣-(2♥)-P-(P); ?, if game was on partner should have shown a sign of life. The 4=4=1=4 hand must move on the 2D auction though, both majors are still in play. Some of this pressure is alleviated by being more aggressive in third seat, and relying on gadgets such as Good/Bad to save our hides when we're too enthusiastic.
  
• I prefer forcing responses to negative ones, and transfers to either. I think the negative free bids make more sense in a limited opener context, but even in that situation I'm not too sure about them.
  
• I think I'm close to freeing up the 2♣ opening in full, but if I do have to include it hopefully I'll only need the 6(+) version. The common version (6+ clubs or 5C4M, approximately 12-15HCP, pass most 11-counts with this shape) seems like a double-edged sword at best and a risk at worst, but I haven't tried it.

helene_t, on 2023-January-01, 09:19, said:

The auction
1♣-1M
2NT
is GF in WJ as opener shows 18+, is that also the case in your system, or can 2NT be passed as opener could have just 17 points?

It shows 17-19 and is GF, since 1M shows 8+. I'm taking it one step at a time and only freeing up the 2♣ opening (if possible), while keeping the 20-21 2NT opener. Down the line I'll see if I can fit that in 1♣ as well (the theoretical advantages are clear), but for now the balanced hands in 1♣ are 12-13, 17-19 and 22+.

[helene_t]

awm, on 2023-January-01, 08:59, said:

1. The Polish 1♣-1♦-1M auctions are really bad. The issue is that this rebid can be either a weak notrump with 3-4 in the major or something like 18-21 with a five card major. While this is nominally non-forcing, the latter hand type requires keeping the auction alive in a lot of places where it can be really dangerous opposite the former.

In this system it's only the 1h rebid that can be 12-13 bal or 11-22 3suited short in a pointed suit, but it's maybe still a problem that
1c-1d
1h-1s
1nt-p
tells opps that we have at most 20 points together so they may be able to double it quite often. I am not sure how bad it is in practice. Maybe responder will also bid this way with 8-11 (31)(45) so that opps don't have that inference.

But I was also wondering if responder shouldn't bid this way a balanced 8-11 which would free the direct 1NT response for something else. It would be kinda cute to play 1NT as a gf relay, for example. The natural 1NT response is needed in WJ where the 1S rebid can be 12-14 with 3-4 spades, but maybe it isn't needed in DD or in this system.

[DavidKok]

That auction doesn't tell the opponents that we are weak, I've had a discussion on that in a different thread (maybe other systems have this 'feature', and that's why it has come up twice?). I've run a simulation including overcalls by the opponents, and on the unopposed auction 1♣*-1♦*; 1♥*-1♠*; 1NT-P the hcp distribution of North-South is approximately as follows:
12 HCP: 0.01%
13 HCP: 0.05%
14 HCP: 0.14%
15 HCP: 0.34%
16 HCP: 0.71%
17 HCP: 1.39%
18 HCP: 11.33%
19 HCP: 26.07%
20 HCP: 19.26%
21 HCP: 9.15%
22 HCP: 11.63%
23 HCP: 13.32%
24 HCP: 6.59%
(Based on a simulation of 435,772,125 hands, on which the auction went 1♣*-(P)-1♦*-(P); 1♥*-(P)-1♠*-(P); 1NT-(P)-P-? 1,000,000 times).
The chance that we have 19 or fewer points on this auction is 40.05%, 3 to 2 odds in favour of having the balance of strength, and the chance that we have 18 or fewer combined HCP is only 13.98% (and sometimes 19 HCP 1NT's come home). Both the 1♦ bid and the 1♠ asking rebid contain intermediate and strong hands as well, which are quite frequent opposite the 12-13 balanced option. Meanwhile the very weakest options bail out (by passing 1♣, passing 1♥, rebidding 2♣, 2♦ or 2♥ or transferring out of 1NT instead of the final pass). Also keep in mind that 1NTXX= is game while responder knows when it's right to run, so you're facing skewed IMP payoffs.

Dutch Doubleton 1♣-1NT is natural (8-10 balanced, desire to hog the hand, usually no 4cM) but it is an awful bid. Most 8-10 hands prefer to bid 1♦ anyway even though systematically you aren't supposed to, and there is no cost when you do choose that route. Plus it is extremely low frequency, and can wrongside 3NT opposite 17-19. My next ambition after eliminating the 2♣ opener is to replace 1♣-1NT with something artificial, though I don't know what would be a good use of it. If you have any suggestions I'd be happy to hear them! My current 2-level structure over 1♣ is:
2♣: Inverted minor, promising 5(+) clubs with 10+ points (usually 6(+) clubs, or 12+ points with 5 clubs and an outside 4-card suit. Balanced hands with 5 clubs can choose to take the slow route with 1♦), may have a 4cM if GF.
2♦: Weak jump shift in either major, constructive opposite 17-19 (approximately 4-7 HCP with a 6-card major, responses are identical to a Multi 2♦ opening).
2♥/2♠: Drop dead in this major (Weak jump shift, approximately 0-5 with a hand unsuitable for game opposite 17-19 bal).
2NT: Drop dead in clubs (transfer), approximately 0-5 HCP with a 5(+) card club suit (usually 6(+) but this is not a strict requirement).

[DavidKok]

I think I've got the system working sufficiently well that I want to share it. It's not optimal by any stretch, but this is not crazy difficult to remember. I'll be tinkering around with making local improvements but I don't think big overhauls are necessary. I also don't have a rebid structure over 1♣-2♣ (inverted minor) with strong hands.

The 1♣ opening contains 1) 12-13 balanced; 2) any semibalanced or unbalanced hand with primary clubs of at least opening strength (no upper limit); 3) 17-19 balanced; 4) any hand that would open a traditional artificial 2♣ opener.
1=4=4=4 hands are a problem and have to improvise - open or rebid notrump, open clubs and reverse into hearts or open diamonds and rebid 2♣, whichever you think is the smallest lie.

Responder's answers are Dutch Doubleton, meaning:

• 1♦: 1) natural diamonds (Walsh); 2) 0-7 any; 3) 8-11 exactly 4♠4♥; 4) (10)11+ balanced with clubs (traditionally only 3=3=3=4).
  
• 1♥: 8+ HCP, 4(+) hearts, natural, may have a longer minor suit.
  
• 1♠: 8+ HCP, 4(+) spades, natural, may have a longer minor suit.
  
• 1NT: 8-10 natural, usually no 4cM, balanced, desire to hog the hand.
  
• 2♣: inverted minor, 5(+)

The meaning of jump responses is up to personal preference.
Over 1♣*-1♦* the responses 1♥ through 2♦ are standard Dutch Doubleton (see link earlier, although I have shifted the NT ladder by a point) and deny holding a traditional 2♣ opener. The 2♣-rebid is wide-ranging NF (approximately 11-17) and shows 6(+) clubs or exactly 4♦5♣. The 2♦ bid shows a club-diamond reverse, approximately 17+ (if responder holds 0-7 we're probably too high here, but this is also the case in Dutch Doubleton). 2♥ and up show the same bid they would have shown on the traditional 2♣*-2♦*; [2♥ and up], in my case Kokish relay with game-ordered rebids. We have a slight edge over standard since responder has limited their hand somewhat - the strong options are unlikely opposite a traditional 2♣ opener (and allow responder to jump/continue bidding at some point), so we may safely assume partner has 0-7 on the subsequent bidding.

Over 1♣*-1♥ the response structure is:

• 1♠: 4(+)♠, 5(+)♣ (or exactly 4=1=4=4) with 12+ points, unlimited, forcing. With this shape you bid this way even if you would have opened 2♣ classically.
  
• 1NT: 12-13 balanced, 3-♥, may have 4♠.
  
• 2♣: 11-15 NF, 5(+) clubs, only 5 on exactly 3=1=4=5 or 2=2=4=5 shape (note: it is allowed to treat those hand types as balanced with suitable cards).
  
• 2♦: Artificial 3-way bid. Shows either 1) A GF hand with 6(+) clubs; 2) A natural club-diamond reverse (16+ so GF) with at most a doubleton in hearts; 3) A hand that would have opened a classical 2♣ (does not promise or deny heart support in this case).
  
• 2♥: Weak raise of hearts, 11-14(15), may be a 3-card suit with an unbalanced hand. I personally prefer to rebid 1♠ with 4=3=1=5/4=3=0=6 hands, but this is up to partnership preference.
  
• 2♠: Shows a hand that would have bid 2♣*-2♦*; 2♠ traditionally. 22+ with 5(+) spades, may have heart support.
  
• 2NT: 17-19 balanced, GF (depending on partnership agreements: may have 4♥).
  
• 3♣: 15-17 with a good 6-card club suit, NF (it is slightly awkward if we miss an 8-opposite-17 game, but the hands have patterned out nicely so we should be able to evaluate the trick-taking potential).
  
• 3♦: A club-diamond reverse with 3(+)-card support (so exactly 1=3=4=5, 0=3=4=6 or 0=4=4=5). Approximately 16-20, weaker than bidding 2♦ (where we would upgrade it to a 'traditional 2♣ opener' due to the suitable shortness).
  
• 3♥ and up: Standard (i.e. non-minimum NF raise, splinters, 3NT 'gambling with an outside stopper').

Over 1♣*-1♠ the response structure is:

• 1NT: 12-13 balanced, 3-♠.
  
• 2♣: 11-15 NF, 5(+) clubs, only 5 on exactly 1=3=4=5, 2=2=4=5, 1=4=3=5 and 0=4=4=5 shapes (note: it is allowed to treat the first two hand types as balanced with suitable cards, I personally don't like doing that with the last two).
  
• 2♦: Artificial 3-way bid. Shows either 1) A GF hand with 6(+) clubs; 2) A natural club-diamond reverse (16+ so GF) with at most a doubleton in spades; 3) A hand that would have opened a classical 2♣ (does not promise or deny spade support in this case).
  
• 2♥: A traditional club-hearts reverse, 4(+)♥, 5(+)♣, ~16-21 (stronger hands go through the artificial 2♦).
  
• 2♠: Weak raise of spades, 11-14(15), may be a 3-card suit with an unbalanced hand.
  
• 2NT: 17-19 balanced, GF (depending on partnership agreements: may have 4♠).
  
• 3♣: 15-17 with a good 6-card club suit, NF (it is slightly awkward if we miss an 8-opposite-17 game, but the hands have patterned out nicely so we should be able to evaluate the trick-taking potential).
  
• 3♦: a club-diamond reverse with 3(+)-card spade support (so exactly 3=1=4=5, 3=0=4=6 or 4=0=4=5). Approximately 16-20, weaker than bidding 2♦ (where we would upgrade it to a 'traditional 2♣ opener' due to the suitable shortness).
  
• 3♥: Does not exist, but it should perhaps be a club-heart reverse with 3(+)-card spade support. Since the 2♥ reverse is not overloaded it's not necessary to split this out.
  
• 3♠ and up: standard (i.e. non-minimum NF raise, splinters, 3NT 'gambling with an outside stopper').

Over 1♣*-1NT the response structure is:

• Pass: Any weak hand that likes the idea of passing.
  
• 2♣: 11-14 NF, 5(+) clubs, only 5 with (31)=4=5 or (40)=4=5, where the opps have a major to run against our 1NT. Partner's 1NT (almost always) contains 4(+) clubs.
  
• 2♦: Artificial 2-way bid. Shows either 1) A natural club-diamond reverse (16+ so GF); 2) A hand that would have opened a classical 2♣.
  
• 2♥: A traditional club-hearts reverse, 4(+)♥, 5(+)♣, ~16-21 (stronger hands go through the artificial 2♦).
  
• 2♠: A traditional club-spades reverse, 4(+)♥, 5(+)♣, ~16-21 (stronger hands go through the artificial 2♦).
  
• 2NT: A chicken bid with 14-15 HCP and 5(+) clubs, NF but responder will often give preference to 3♣.
  
• 3♣: GF with long clubs, 16-20 (stronger hands bid 2♦)
  
• 3♦ through 3♠ and 4♣ do not exist, but could be filled with e.g. very strong 1-suiters (equivalent to traditional 2♣*-2♦*; 3X).
  
• 3NT: 17-19 bal or a strong unbalanced hand that doesn't want to try 5m or slam.

Over 1♣*-1M; 2♦* the responses are mostly natural, but some are not. The structure is based on Erik Sjölstrand's version of Odwrotka, who based it on Jassem's Odwrotka Strong Heart (that I've taken out):

• 2M: A 5(+)-card major.
  
• 2oM: Exactly a 4-card major in a balanced hand (may have 4♠4♥ 12+ on 1♣*-1♥; 2♦*).
  
• 2NT: Does not exist.
  
• 3♣: 4M5(+)♣, 8-11 (12+ would have responded 1♣*-2♣)
  
• 3♦: 4M5(+)♦, 8-11 (ditto)
  
• 3M: 7(+)M, sets trumps and demands cuebidding. May be bid with a solid 6-card suit if the hand is suitable.
  
• 1♣*-1♠; 2♦*-3♥: 5(+)♠, 4(+)♥. With 6♠4♥ the space-saving 2♠ is usually better, so maybe this should show 5♠5♥.
  
• 1♣*-1♥; 2♦*-3♠: Does not exist, with heart-spade two-suiters start with 2♥ (in case partner has the club-diamond reverse we want to identify the misfit at a low level. Keep in mind partner doesn't have 3-card heart support for that option).
  
• 3NT: Does not exist.
  
• 4♣: 5(+)M, 5(+)♣ - You may instead choose to bid 2M and then bid and rebid clubs on the next round.
  
• 4♦: 5(+)M, 5(+)♦ - A risky bid since 3NT might be best opposite long and strong clubs, normally you'd bid 2M and then bid and rebid diamonds on later rounds.

Over 1♣*-1M; 2♦*-3X (or higher) bidding is natural, with fourth suit artificial available where relevant.

Over 1♣*-1M; 2♦*-2X the rebids are:

• 1♣*-1♥; 2♦*-2♥; 2♠: Does not exist (strong spade hands would have jumped to 2♠ last round). Could be used as artificial with 3(+)-card support.
  
• 1♣*-1♠; 2♦*-2♥; 2♠: Does not exist. Could optionally be used as 4-card spade support, asks responder to pattern out.
  
• 2NT: 22+ any, forcing through 4♥ (so after this bid 3NT by either side is forcing). Safe since we have ~22+8 HCP at minimum. It might be wise to make this forcing through 4NT, and give up on playing 4♥/♠ here. Responder bids extra length up the line (with the 5(+) card major: a 4(+)-card minor, sixth(/seventh/etc) card in the major suit, or 5332 with 3NT. With the balanced hand: a 4-card minor, or 4333 with 3NT. After this opener's rebids are natural and show 5(+) in the suit bid, or confirm a fit in a previously shown suit. All other hands bid a forcing 3NT).
  
• 3♣: 17-21 single-suited clubs, may have support for responder's major. Subsequent bidding is natural.
  
• 3♦: 16-21 clubs-diamond reverse with at most a doubleton in support for responder's major. 3oM asks opener to bid 3NT, all other bids are natural.
  
• 3M: Sets trumps and initiates control-bidding. It is usually better to bid 2NT instead. Optional: have this show a major suit fit with a strong clubs hand instead.
  
• 3oM and up: Do not exist, 2NT has to be better than jumping here.

Over 1♣*-1NT; 2♦* there is room for responder to pattern out. I haven't given this much thought, I think either coded responses (2♥ = 4(+) clubs, 2♠ = 4(+) diamonds, etc, all natural) or shortness-showing major suit bids (2-) would work well. Complete shape-showing relays for 1NT-2♦* (art GF) exist, that could work well here.

During some practice hands I ran into a few questions that I don't know the answers to. In no particular order:

• With (semi)balanced 22+ with 5♠ opener can choose between 2♦* and 2♠ on 1♣*-1♥. I don't know which is better. Responder will frequently rebid 2♠ over 2♦ or 2NT (natural) over the direct 2♠, so either option carries a significant risk of wrong-siding the contract.
  
• Flipping the meanings of 2M and 2oM over 1♣*-1M; 2♦*-? will right-side the contract more often, at the cost of being less natural.
  
• Responder might wish to rebid 2NT with some very shape-oriented hands over 2♦, right now the bid is not in use. The most suitable hand type would be a hand with long clubs, since we are never stopping in 3NT when opener has a clubs/reverse type hand with those. However, simulations show those hands are such low frequency that we may as well not bother. 4M5(+)♦ hands are interesting but will wrongside 3NT opposite the GF single-suited clubs hands. If nothing else it makes sense to fold the 5-5 hands in there, so we can stop in 3NT (we lose that option by jumping to the 4-level immediately). Alternatively it can show 12+ any, limiting all/most other responses, but I like bidding shape before strength, plus we either create a force past 3NT next round or opener limits the hand anyway.
  
• Several of the natural patterning out sequences can be compressed and optimised by frequency or game order, I've chosen not to because 1) it's a new system and 2) these auctions are very low frequency, I don't want to have to memorise them.
  
• With both majors opposite strong single-suited clubs the scheme above has a bit of nasty guesswork, i.e. 1♣*-1♠; 2♦*-3♥ (at least 5-5? Or also 5-4?) and now it is unclear whether 3NT, 4M or 5♣ is best, or even if slam might be on. There might be ways to fix this, but note that traditional systems with Ingberman over reverses bid the same way. I don't feel too troubled by this.

[nullve]

DavidKok, on 2023-January-02, 07:51, said:

Over 1♣*-1♦* the responses 1♥ through 2♦ are standard Dutch Doubleton (see link earlier, although I have shifted the NT ladder by a point) and deny holding a traditional 2♣ opener.

From that other thread:

DavidKok, on 2022-August-28, 12:52, said:

Then over 1♣-1♦ you have:

• 1♥ - any 11-13 balanced or natural hearts+clubs not balanced (4(+) hearts, 5(+) clubs or exactly 4=4=1=4)
  
• 1♠ - 4(+) spades, 5(+) clubs, max 18 (I still play 2♠ as a strong jump shift here, but you can well do without).
  
• 1NT - 17-19 balanced
  
• 2♣ - 5(+) clubs, not balanced
  
• 2♦ - strong reverse etc.

If opener rebids a natural suit your normal agreements are in place and the bidding resumes like standard. Over a 1NT response it is easy to play system on, and I do. Over the 1♥ response we need another round of agreements:

• pass - 0-5 with a preference for hearts over clubs
  
• 1♠ - relay, tell me which type you had (answers are 1NT 11-13 balanced, 2♣ 4♥5(+)♣ 10-16 or so, 2♦ artificial 4=4=1=4 or 4=4=0=5 11-16, 2♥ 5♥6♣, 2♠ 4=4=1=4 or 4=4=0=5 17+, 3♣ stronger than 2♣).
  
• 1NT - 4=4 majors 6-11 NF
  
• 2♣ - natural ♦+♣ weak
  
• 2♦ - weak and natural
  
• 2♥ - 5-7 5(+)♥ NF

You tend to almost always bid 1♠ so the other bids show hand types that are ill-placed over hearing a 1NT response (over which we play system on).

This is strikingly similar to stuff you sometimes see over 1♣-1♦ in T-Walsh!

[DavidKok]

Yeah, it's also relatively popular to play T-Walsh over a Dutch 1♣ opening here, and the response structures are nearly identical. I've spent quite a bit of time comparing the Full Dutch Doubleton and T-Walsh, and I think they are about equal when it comes to results. T-Walsh wins on stopping in 1♠ with weak hands opposite a minimum, but pays in having to pass 1♣ with a weak hand without clear direction and no major (e.g. weak with both minors, or weak with one minor but no desire to play at the 2-level). This mostly comes up when partner is 17-19, the opponents tend to rescue you when partner has (11)12-13. The Dutch Doubleton also puts on way more pressure, in that many sequences are ambiguous about responder's strength while clarifying opener's strength neatly.

I wouldn't be surprised if you can take this artificial 2♦ rebid and copy paste it straight into a T-Walsh structure. You just have to worry a bit that partner may have a lousy hand with a long major on 1♣*-1red; 2♦*, so you'd have to include an artificial brake (maybe the free 2NT rebid since it's probable game isn't on - or 2M NF, with 2NT being 5(+)M forcing).

P.S.: I spotted a mistake in that quote, 1♣*-1♦*; 1♥*-1♠*; 2♥ doesn't show 5♥6♣ but rather just shows a club-hearts reverse (approximately 16-20), while the direct 1♣*-1♦*; 2♥ is reserved for a monster (20+ with 4♥5♣+) in DD. My mistake, I think I did get it right in this thread.
P.P.S.: I've found some fascinating weak options for the freed up 2♣, although it is unsurprisingly difficult to find good suggestions since most people use these as weak-or-strong bids (so that 'weak with clubs' is generally not an option) or can't afford to include a weak option at all (e.g. Polish or strong club/diamond systems). If you have any suggestions or wild ideas I'd love to hear them.

[nullve]

DavidKok, on 2023-January-03, 04:48, said:

T-Walsh wins on stopping in 1♠ with weak hands opposite a minimum, but pays in having to pass 1♣ with a weak hand without clear direction and no major (e.g. weak with both minors, or weak with one minor but no desire to play at the 2-level).

In my version the bidding would go

1♣-1♠*
1N**-P***

* helene_t's trick: does not include an invite opposite the split range 11-13(min)-or-17-19(max)
* includes both 11-13 BAL and 17-19 BAL!
*** 0-6

on the hands you mention, and Responder would have little incentive to pass 1♣ even if the opening didn't include 23+ BAL or GF hands.

[DavidKok]

Do you directly bid at the 2-level with all minor suited hands? Or do you have a gadget to split 11-13 from 17-19 on the auction 1♣*-1♠*; 1NT*-[some bid showing a minor suit, 1- or 2-suited]? And can you stop in 2♣ and 2♦?

[nullve]

DavidKok, on 2023-January-04, 05:29, said:

Do you directly bid at the 2-level with all minor suited hands? Or do you have a gadget to split 11-13 from 17-19 on the auction 1♣*-1♠*; 1NT*-[some bid showing a minor suit, 1- or 2-suited]? And can you stop in 2♣ and 2♦?

In helene_t's version, 1N is always (12-14 or 18-19) balanced, iirc. I suppose you could play 2m as NF (to play?) opposite 11-13 but GF opposite 17-19 over that.

In my version, 1N is more Gazzilli-like and either balanced with 11-13 or 17-19 OR unbalanced with either "10-12" or "16-18". Over 1♣-1♠; 1N, Responder will currently pass 1N with all 0-6 hands and bid 2♣ on all unbalanced GF hands with primary diamonds, but I suppose 2♣ could be made to also include 0-6 hands with 6+ D that intend to pass Opener's otherwise GF relay (2♦).

[helene_t]

nullve, on 2023-January-04, 07:46, said:

In helene_t's version, 1N is always (12-14 or 18-19) balanced, iirc. I suppose you could play 2m as NF (to play?) opposite 11-13 but GF opposite 17-19 over that.

Yes, that was my idea.

[nullve]

The system Bocchi-Duboin played in the 2001 Bermuda Bowl:

convention card
notes to convention card

Obvious tweak to make it resemble your system more:

1♣: either 12-13 or 23+ if BAL
1♦: always unBAL
1N = 14-16 BAL
2♣ = 17-19 BAL (the easiest way to make 1♦ unBAL)
2♦/♥/♠ = ?
2N = 20-22 BAL (since you don't like Multi)