[ArtK78]

Zelandakh, on 2012-October-10, 07:05, said:

The scheme I posted in the other thread could handle this

5NT = ace (6♣ asks if extra length)
6♣ = king (6♦ asks if extra length)
6♦ = queen
6♥ = none
6♠ = KQ
6NT = AQ

So with KQx the response would be 6♠, or with Kxxx the response is 6♣, then 6♦ finds the 4th heart.

Yes, this does the trick.

Of course, all of these posts relating to 5NT as the Grand Slam Force in this sequence assumes that partner will interpret 5NT to be a Grand Slam Force. While a plausible meaning, it is not free from doubt. In my many years playing this game, I have seen only a handful of 5NT calls which were unambiguously a Grand Slam Force (and, quite frankly, not that many that were not a Grand Slam Force). Given the amount of time and effort that players have spent discussing and refining their scheme of responses to the Grand Slam Force, it remains a rarely used convention.

[ggwhiz]

aguahombre, on 2012-October-09, 21:50, said:

Not being familiar with the OP's 4th-chair treatment of the 3C opening, which I happen to like even though I haven't thought about it before ---I made some assumptions, which may or may not be those of the OP.

The assumptions were about responder's options at the point he bid 5H. It should be a FP situation, IMO; and, with Pass, double, and 5/6M available it would seem that a major-suit freebid would absolutely contain 4 of that suit.

If the possibility responder only has 3-card support is real, then it would even change what 5NT is needed for.

Yeah, sorting out these methods was too tough for me, I just thought 5♥ on kxx or kjx would be justified depending on the rest of the hand.

[kgr]

aguahombre, on 2012-October-09, 21:50, said:

Not being familiar with the OP's 4th-chair treatment of the 3C opening, which I happen to like even though I haven't thought about it before ---I made some assumptions, which may or may not be those of the OP.

The assumptions were about responder's options at the point he bid 5H. It should be a FP situation, IMO; and, with Pass, double, and 5/6M available it would seem that a major-suit freebid would absolutely contain 4 of that suit.

It is a GF opening and responder has 0 to 11 pts.
We don't have good agreements about FP, but we would not let the opps play 5D after they have first both passed and partner opened GF.
So yes, it is a FP.
Opener showed at least a 5-5, but I agree that responder very likely has a 4-card.

aguahombre, on 2012-October-09, 21:50, said:

If the possibility responder only has 3-card support is real, then it would even change what 5NT is needed for.

This makes me wonder if I want to agree something with my partner about this situation
Seems to be too specific, not frequent enough and too costly to have an agreement with misunderstandings.