Posted 2014-December-04, 07:55
First things first. When I have seven diamonds and five spades, partner will have his work cut out for him to convince me the hand belongs in NT. I would probably bid 4D over 3NT even without a 4C bid, and I certainly would do so after the 4C. It could be right to play this in 3NT, but after 4C that option doesn't exist and so I bid 4D.
As to the opponent's 2H bid, who knows? You describe them as weak. It's a relative term but my guess is that most pairs have not discussed the meaning of their 2H bid when the opponents have bid spades to show hearts, and they cannot explain a bid they haven't discussed. My guess is that it shows hearts, and the club bid shows clubs to go along with their hearts. But still, who knows?
Anyway, I bid 4D directly over 4C. And if for some reason I pass 4C, I pull the double. Undiscussed, I think that passing 4C and then pulling the double to 4D is weaker than bidding 4D directly over 4C. No doubt this could be a huge misfit all around and no one can make anything, but I am bidding my diamonds. If after that they go on, and then partner doubles, then I pass. I think at that point it is his choice.
Ken