Thanks for the interesting replies so far, some food for thought.
Tramticket, on 2019-January-08, 02:21, said:
Our one-level openings include 20 HCP hands and our 2NT rebid is forcing to game.
Our auction would start:
1♦, 1♠; 2NT, 3♦; 3♠ ...
Having identified the double fit, at the three-level, in a game forcing auction, we would exchange cue bids and hopefully reach the small slam.
Much the same here. With regular partner I would probably have chosen to open 1
♦ and although our 2NT rebid is non forcing I would use it anyway (he knows it promises 18 hcp) - so our auction would start the same way and probably proceed:
3
♠, 4
♣; 4
♦, 4
♥; 4NT, 5
♥; 5NT, 6
♦; 6
♠, P
The_Badger, on 2019-January-07, 16:33, said:
Happy to let you say it
Although to be fair the bid does imply mild slam interest, as we agreed to play 4-level "Texas" transfers too.
The_Badger, on 2019-January-07, 16:33, said:
4♦ if not recognised as an advanced cue bid (by agreement) should show a second suit ♦s and at least 6♠s as willing to play opposite a doubleton.
Showing a good second suit and implictly some slam interest is how 4
♦ is usually understood around here, too. It's logical and is coherent with what happens over 1NT, but tricky because you need some agreement about what each 5-level bid by opener would now mean and which if either of responders' suits is treated as trumps.
heart76, on 2019-January-08, 01:07, said:
2nt - 3♥
3♠ - 4♣ cue, which actually promises only 5 ♠
4♦ confirming 3+ ♠ - 4♥ with the aim to cue and not use RKCB.
That's why I like much better Cyberyeti's 4♦ from opener.
So if I understand correctly, you play that new suit by responder after a transfer is a control-bid fixing trumps in the transfer suit and showing slam interest, rather than showing a second suit or a shortage.
I think that would make a lot of sense over 2NT, where otherwise the control-bids start too high to cut much ground. Although good luck convincing my partner to give up showing a natural second suit.
Cyberyeti, on 2019-January-07, 16:32, said:
2N (good 19-21) - 3♥
4♦ (at least HHxxx♦Hxx♠) now S is REALLY interested (we use 3N/4♠ for 4 card support breaks)
Opener using the other suits to show a good 5-card suit is intriguing, and I guess is going to find some 5-3 second-suit fits that responder showing his 4-card second-suit will not detect. On the downside, it's not great to have the strong opener rather than the responder describing his hand, particularly when the responder might not be interested.
Do you play this over 1NT too? At first sight I would be worried to play this over our 15-17, forcing to 3-level when we might have 5-3 fit and half the points.