George,

  Aft-raking the masts might be a mixed bag.  The benefits would be more clear-cut on a cat where you can balance out all the forces, but less clear-cut on a proa where aft one one shunt is fore on another.

  You could definitely get a great sailboard-like sail shape, but the build cost would be higher than a straight circular mast, and it would be harder to trust the boat to tend to itself while on the hook in a gale.

  The bigger issue with moving the COE aft, though, would probably be rounding up.

  Since the boat has to go in both directions, it's useful to move the COE closer to the center in order to keep the forces on the two rudder/foils more equal.  That would result in better flow over both foils and cut down on weather helm (and the rudder needed to counter it).

  This is particularly noticeable when going to windward at low speeds where the foils don't have much to work with.  At some point the forces causing the boat to round up overwhelm the rudders and the boat stalls.

  There's an extensive discussion of this in the forum from 2011.12.30 through 2012.01.10.  Rick actually found it was better to sail with the windward hull to leeward in extremely light winds because of the rounding up due to:  a) Rig COE being aft of the boat's CLR, and  b) drag from the windward hull.

  I can see that having mast weight aft would help raise the "bows", and the canted masts would do this, but I'm not sure that would be worth moving the COE aft as well.

        - Mike