Bleah. Now I remember why I stopped playing with the sort of partner who would perpetrate such a bid. (In fairness, it could be right, but there's no particular reason to believe that on BBO, which I think you said is where you play.)
4H should show self-sufficient hearts, no side four-card suit, and no slam interest -- certainly no first-round control in either pointed suit. The problem, of course, is that it doesn't necessarily show that this time, and in any case that still doesn't answer the question. All you need for 6C is KQ AKxxxxx xxx x, which is consistent with the auction, and in general if a perfect minimum makes it cold you need at least to look for it. So yes, you need at least to look for slam.
I suppose 5D's being key card for hearts excluding diamonds (RKCHxD in all my notes...) is too much to hope for...
Clubs will be trump, unless partner corrects, which he
should do only with solid trumps and a doubleton club, though he probably will with a solid suit and a single club (and you're not getting a club lead unless RHO is Zia, anyway). The likelihood of a club void, or imperfect hearts (no queen) that don't break, is too great to risk it. (The latter risk alone would be insufficient at MPs.)
Plan 1, the practical but theoretically wrong one: 4NT, whatever flavor of ace-asking you're using. If missing two key cards, try 5H. Yuck. Bleah. Awful. But still probably making, and only missing a good slam about 40% of the time.
Plan 2, the theoretically correct one: 5D, and let partner decide.
Plan 3, the practical plan at IMPs anyway: direct 6C, then glower at partner when he corrects to 6H with KQx AKQJT98 xxx --, or to a grand with KQ AKQxxxx ATxx --.
Plan 4, the creative one, which I think I would try: 4S, then 6C over almost any response. You're pretty well forced to slam, you're probably not finding a good grand anyway, and this minimizes the probability of being dead by trick two. Bad if partner corrects to 6H, bad if he bids a grand without the spade ace, but even then you're only dead if they lead spades, and it would be very normal to try to cash the diamond ace here. (If LHO doubles, I'd try correcting to 6H, putting his partner on lead, unless playing against really good opps in which case I'd just take my lumps. And if RHO doubles, 6C is going down on a club ruff so I correct again...)
Last edited by atakdog; 04-24-2008 at 01:40 AM.
Reason: typo