[lowerline]

Kaplan Inversion (aka Granville) =

1♥ - 1♠ = at most 4 spades
1♥ - 1NT = at least 5 spades

After 1♥-1♠ the 1NT rebid shows exactly 4♠5♥ in a hand not strong enough for a reverse of 2♠, so this is not forcing.

My question now is: how do you rebid with 4♠6♥?

[MickyB]

I'd be inclined to make 1NT forcing and bid 1NT on these hands. Usually you'll be happy to play in a 5-2 ♥ fit or a 4-3 ♠ fit. Even if 1NT is NF, it is still my bid on 6♥4♠.

[inquiry]

I recently added kaplain inversion again, but I have a number of other unusual agreements, so here goes.....

First, for me, 1H-1S will never hold 3♥ unless GF with 4 spades. Second, weak hands with 3♥ will raise directly and invitiational/GF hands with 3♥ would go through an artifiical 2♣ response (or 3NT response). So a fair number of hands are removed from the mix.

1H-1S-1NT = shows Hearts and diamonds or hearts and balanced upto 13 hcp. 2♣, 2♦, and 2♥ by responder are not forcing (and 2♠ is artificial GF).

1H-1S-2C = ritong 2♣, showing several types of strong hands (but not two suiters, but can have a side four card suit-- including spades.

1H-1S-2D = four card spade support (not diamonds, see 1NT) can have 6H (your point)

1H-1S-2H = six plus hearts, no four spades, not balanced, not 4+ clubs (we open 2M with minimum opening hands with 5+major and 4+clubs)

1H-1S-2S = true reverse plus five spades, 6 hearts (with 4 spades, go through ritong 2♣

The problem with this is partner with weak hand and clubs, might have to signoff in 3♣ rather than 2♣.

[Gerben42]

I'd respond 2♥ with minimum hands and 1NT with a little extra. Note that although 1NT is not forcing, it won't be passed that often.