johnu, on 2019-June-17, 03:29, said:
IMHO when responder has a 6+ card suit in the near slam range, having a good fit is more likely to get you to a good slam. The best way to do that is with a splinter so opener can evaluate how likely non trump honors are going to have full weight.
The more you know about fit the better it is, of course. Responder with a 4+card side suit would (in our methods, at least) have shown it as a game force after the Jacoby transfer. So if he is control-bidding directly he probably has a single suiter, which is more than 50% likely to have no singleton or void (see the hand of this thread as an example), whereas it will always have honour controls.
johnu, on 2019-June-17, 03:29, said:
I'm also not sure what opener is supposed to do with the knowledge that responder has an outside control. If you have controls in all 3 non trump suits, are you supposed to bid a slam? bid RKC? continue cue bidding even though you have no idea if you have wasted values opposite shortness?
A full reply would need a book, "Slam a tempo di cue bid" by Petroncini and Belladonna being a good start. I think you are quite capable of answering your own question about what knowledge of controls and fit is needed to bid a slam or when the probabilities do not justify bidding beyond a certain level of trumps. Yes, opener can RKC over the first control-bid of responder, although that would usually be a poor idea - continuing to control bid he will still find out about any missing trump honours and have a better chance of getting things right when partner has a void.