I figured most people wouldn't overbid as badly as I did, so finessed in a gamble for the contract and resigned myself to down 2 when the finesse failed.
But it turns out East was caught in a weird cross between a Morton's Fork and an Endplay. Play the Ace of Diamonds, and I have enough winners in board to dump all my club losers (with East forced to give me the entry for it on the next trick). Shift to a heart or a low diamond to avoid giving me two diamond tricks, and I instead get to dump my diamond loser away.