Obviously it is helpful if 4
♠ is keycard here (kickback). It may be worth trying a 4
♠ cue instead if 4nt would be keycard.
It would not really occur to me that partner might have x KQJxxxx x QJxx. Would you really overcall at the four-level on a hand that's not worth opening at the one-level? Yes, I'm sure there are many hands where you'd make a 4
♥ preempt, but I think the disciplined approach is not to bid 4
♥ on these hands, since if you do partner can never figure out when you have a good hand? And with RHO sitting there with four spades and three aces I think he might find a spade raise?
As for Kx AQJxxx x QJxx, this is not exactly possible since
we have the spade king. Change the spade king to spade ace and 5
♥ certainly has play (it does need the heart finesse though).
It wouldn't particularly bother me to be in slam opposite Ax KJT9xx Ax AQx or the like, and we can play 5
♥ in any case (we are not forced to slam off the heart queen), which is essentially cold.
So basically:
(1) I disagree with your evaluation of the worst possible hands for partner. I think the worst realistic hands for partner put 5
♥ on a finesse. If by bidding keycard, I deter partner from bidding 4
♥ on x KQJxxxx x QJxx in the future, this is a
good result of bidding keycard.
(2) Yes, there will be hands where we end up in 5
♥ on a finesse and it goes down. And there may be hands where we reach 6
♥ on a finesse and it goes down. But there is a flip side to this business of "you should be conservative in case partner has a bad hand so as not to deter partner from bidding" -- if you routinely take conservative actions like this and miss lay-down slams, partner will start jumping to
five hearts on the likes of Ax AKQxxx Axxx x because, after all, he knows you will pass on a full opening bid with a singleton spade if he bids "only" 4
♥. Forcing partner to jump to the five level on moderately good hands like this one could be costly too couldn't it?
Adam W. Meyerson
a.k.a. Appeal Without Merit