[lycier]

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Now you can see
1- 4♦ shows " 2+♥,17-20TPs ", it is impossible.
2- Gib has no way to show limited raise in this hand.

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Here basic Gibs play rediculous defense in this hand without same bidding sequences.

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[Bbradley62]

What would be the point of showing a limit raise? If you have a limit raise, you bid 4♥ because you know that you have enough to be in game and not enough to be in slam, given the description of 3♥. I agree that the cut-off between 4♥ and 4♦ should be less than 16 vs 17; maybe 13 vs 14, so that 4♦ shows slam interest opposite a maximum 3♥ bid.

[lycier]

Very strange doubting.

Now let's study Gib CC together.
After 3♥, the following Gib CC for east player are
- 3♠= 1-♥,4+♠,11-20TPs.
- 3nt= 4-♥,4-♠, 13+hcp,20-TPs,stop in ♦.
- 4♣= 1-♥,17hcp,twice rebiddable ♣,15-20TPs.
- 4♦= 2+♥,17-20TPs.
- 4♥= 2+♥,10+hcp,11-16TPs.
- 4♠= 10+hcp,strong rebiddable ♠,11-16TPs.

Obviously there are too many impossible bids. We know Gibs never play showing-fit cuebid, so there is a necessary matter left here - How to show its limited raise with 3-card fit in the 11+hcp/11+TPs hand?
Now only way left is cuebid 4♦ with slammish.

Maybe this is a helpless choice on Gib CC, otherwise it will bring many huge difficulties on the programming.Of course, this is my guess.

[Stephen Tu]

lycier, on 2016-June-11, 20:56, said:

Obviously there are too many impossible bids. We know Gibs never play showing-fit cuebid, so there is a necessary matter left here - How to show its limited raise with 3-card fit in the 11+hcp/11+TPs hand?

BBradley told you: 4♥. There are also some slightly weaker hands and hands with only 2 cds that may raise to 4♥ also. There's little risk of missing slam with this range opposite a partner not strong enough to double first or jump to 4♥ themselves. There's also little room to distinguish between ranges because of the preempt, as a consequence, min raises to 4♥ and hands of this strength have to share a bid. Over preempts you don't have the luxury of breaking down raises into super tight ranges, the main thing is "bid game or not", and "try for slam or not". At the margins when both people are maximum and conservative, you might miss a slam, that's why people preempt, it disturbs your accuracy.

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Now only way left is cuebid 4♦ with slammish.

And he agreed that the range for the 4♦ cue bid should be lowered given that East is a passed hand and can't really be that strong.

Obviously these bid definitions should be adjusted to account that East GIB is a passed hand, so you don't have to account for the super strong hands in its ranges.