That's your problem right there. North doesn't know how to make catamaran sails. You're not going to get much advice from racers, because only Hobie sails are class legal.

Not to be a smart butt, but the shape that Hobie gives them works pretty well. The top is fairly flat, since the mast gives you most of your camber. Downhaul frees up the leech. Outhaul does next to nothing. Oversheeting will stall the top of the sail. You need to have tell-tales high up on the sail and a couple on the leech to tell you when you're oversheeting.