TWOfer

I agree with the 2D! = artifical, nmf [ You need one way to force and others as non-force]. Thus, 2H instead by Responder would be non-forcing showing 5s/4h. But after 2D! , I agree with the 2H by Opener showing a 5+c/4h as a hand not worthy of a reverse or a 3H-jump ( eventho max for the 2C rebid) since x x x x just barely passes muster as a 4 card suit. Now, i think Rado covers it best. 2S should be another one round force just in case Opener has 3 cards Sp ( rebidding a 4card H suit is 1st priority), and the 4C-jump bid best shows Opener's "max" hand w/good Cl. Lifemonster continued best with the 4H! and 4S! cuebids respectively. Now here is where it gets tricky. After 4S!, if you are playing a European cuebidding system, then 4NT! by Responder ( after 4S) = another Sp cuebid. South ( Opener) then confidently bids 6C knowing his chances are good.