A neat solution would be to let opener's 3-of-a-suit rebids on this
auction all be transfers, all promising extras. (3S would show a
strong balanced hand with four diamonds and xxx or xxxx of clubs.)
This hand would then be an easy 3D bid, knowing you will get another
chance to call even if partner tries to sign off in 3H.
The problem with this approach is that it would make opener's rebids
after 1D-(2C)-X different from after other negative double sequences.
But this is the only negative double of a simple overcall where
responder does not promise a known suit, so it's a special case. (I
suppose you could try to do something similar with 1C-(2D)-X, but you
might give up the natural 2NT, and thus you'd need to be willing to
rebid 2H or 2S on three-card suits--something like 2NT = clubs,
extras; 3C = clubs, minimum, 3D = hearts, 3H = spades, 3S = balanced
with 4-5 clubs and no diamond stop.)
Christopher Monsour