ggwhiz, on 2012-December-31, 12:51, said:
I HATE the idea of telling them the diamond finesse is on before they pick the final contract or line of play with AQ to length opposite a stiff.
Conditionally, LHO has already decided on the final contract: he's about to bid 6♠
opposite sufficient key cards. He must has at least 3 key cards to bid 4NT in this auction; RHO has shown one and they won't be trying for grand as we hold the other key card.
If dummy has an undisclosed singleton opposite AQ to length, declarer won't be worth his 4NT bid but the contract will be cold anyway.
I hate the idea of making partner guess which suit to lead from when I might be able to help.