[arigreen]

As many people have pointed out, GIB's system is incomplete following a 2N rebid by opener. I am open to suggestions for what GIB should play in this auction. I am looking for something that is mostly natural and as close to standard as possible. (but there doesn't seem to be any "standard" for this auction)

My proposal is below. Feel free to suggest alternatives such as Wolff, etc.

1m-1M-2N:

3m = natural, forcing
3Om = "new minor forcing." Promises 5 cards in the major
3M = natural, forcing promises 6
3H (over spades) = 5-5 majors forcing
3S (over hearts) = 4-4 majors forcing
3N = to play

1C-1D-2N:
3C = nat. forcing
3D = nat. forcing
3H = 4 hearts, longer D, forcing
3S = 4 spades, longer D, forcing
3N = to play

1H-1S-2N:
3C = artificial checkback (promises 5S)
3D = nat. forcing
3H = nat. forcing
3S = 6 spades, forcing

[Echognome]

Sounds pretty reasonable to me. The premise seems that all weak hands just pass 2NT.

I think you could even just play that all bids are natural and forcing, with 3M showing a 6-card suit. You bid 3m with either 4-5 or 5-4 and if partner has support, partner can clarify it for you on the way to 3NT.

[barmar]

Sounds fine to me, too. It's pretty much what I play with most partners in real life, except when I play Wolff Signoff.

[Jlall]

Yeah that's fine.

meepmeep

[paulg]

My answer depends slightly on the aim of developing GIB's bidding.

If it is to improve GIB's bidding when partnering GIB, then some artificiality akin to normal tournament methods, such as checkback or even nmf, is a reasonable approach.

However if the aim is to improve GIB's bidding with a human, then a more natural approach may be better. At my local (UK) club the number of pairs using checkback or nmf over a 2NT rebid can be counted on one hand. I would expect this to be true for most of the UK outside the top 20% of tournament players. Wolff sign-off is practically unheard of here in any context.

BTW, I think your proposal is fine for the artificial approach

[helene_t]

GIB already plays NMF over a 1NT rebid. Of course the situation is slightly different over 2NT since you can play all actions as GF and therefore might not need an artificial force. Anyway, I think lots of humans will assume NMF over 2NT if they also play it over 1NT.

[awm]

This is what Elianna and I play. Something more complicated might be better in principle (i.e. transfers), but the suggested approach is a nice blend of simple and reasonably good.