DavidKok, on 2021-February-08, 03:13, said:
On a typical auction 1m-1M; 2M-? having some agreements will help. Personally I allow opener to raise with only 3-card support and an unbalanced hand, which is fine at IMPs and (in my opinion) really good at matchpoints. However, this has some downsides for the subsequent auction, in particular I use the cheapest available bid as an artificial shape-asking bid. Anything else promises either a 5-card major or willingness to play 4M in the 4-3 fit.
Without such an agreement, I think it is relatively standard to play:
- 2oM (only spades over hearts)/3X (new suit below 3M): A help suit trial for 4M, asks if partner to bid game with values in the bid suit, or an advanced cue.
- 2NT: Forcing game try, suggests 3NT despite the major suit fit.
- 3m: Any other game try - promises support by negative inference, so typically a double fit. Forcing.
- 3X/4Y (new suit between 3M and 4M): Splinter for M.
- 4m: A double fit and slam-going hand.
It would be rather non-std in America. Here, I think standard without agreement is:
3M/2nt - NF GT, natural
3m - forcing GT with fit, maybe slammish
4m - splinter (NOT double fit)
3nt - choice of games
But with agreement a lot of players play 2nt as a forcing inquiry, either simple 3344 convention or more complicated "spiral" variants. (It is unclear to me whether 3344 is "spiral" or not, I have heard people call it spiral but IMO spiral should refer to more the more complicated response sets)
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If you are slammish despite opener only being able to give a simple raise you could jump to 4m, showing a big double fit. But there is no real downside to bidding 3m first and then making a cue bid on the second round, which is what I personally prefer.
It's rather useful to be able to splinter in openers minor when opening on xxx suits is possible.
The homebrew scheme I prefer is non-standard, after 1m-1M-2M:
2nt/3m/3M - all non-forcing, natural game tries. (If 2M can be 4-3 fit, I don't see why have to be forced to play 3M if responder can have huge minor fit and it's just safer to play 8/9/10 minor fit in a cozy 3m instead of Moysian)
cheapest new suit = GF shape inquiry, either looking to relay out opener's shape to evaluate slam or choice of games, or 4cd M stopper only in this suit. This route to possibly get back to 5m/6m/7m.
higher new suit = 4cdM only, stopper, no stop in other suit, choice of games.