Jake,
You are a man of action to race all those distance races. respect, to all the adventurers.

what SewSew has going for it is the light weight long narrow main hull. fineness ratio is key in displacement boats.
He can both paddle and sail with great efficiency, most likely. I think he is able to balance on 1 hull a lot. A twin hulled catamaran can't do that in paddling conditions, so more drag.
A fast cat should be able to do better in the open Gulf winds though, i would guess.
Perhaps the long narrow light weight hull plus 1 ama could be a solution? A tacking proa of sorts that you put a rack and trapeze off the main hull to take some of the load off the ama when it is to leeward. Yet when you are paddling the ama would have very little drag.
Kind of the less is more theory.