A harryproa would have the rig in the lee-hull and the windward hull (what would be the ama on a traditional proa) swollen to include all accomodations. This puts maximum weight to windward all the time, which is good for cruising. The harryproa would never have problems coming about, and the overall windage might well be less with accomodation in the deep ww hull and no clunky bridge-deck windage or bridge deck stuff that might intercept a wave from under or over. The lee hull would be just for carrying rig and cutting through water, the ww hull occasionally lifted a bit under press of sail thus some reduced drag (at times) ---- and so I am saying a harryproa vs. a catamaran might need a reasonably complex comparison-anaysis.
Contact Rob Denney for his views of this -- he is a nice guy and knowledgeable -- or join the Yahoo Harryproa group. The Yahoo Proafile International group discusses harryproas sometimes but usually with a little warmth from a definite minority of the membership. --Wade