RE: Double fins?
Friend of mine has a HiFly Madd twin fin. He likes it; I don't.
I prefer my C131; just got an Aero 117, which I will have to test ride ASAP and can't comment vs twin fin at this point.
I concede that if you insist on using big sails, in really shallow water, it's probably a decent option. Otherwise, I'm skeptical.