Chip Buck of Whirlwind Sails has made some amazing sails that I have seen first hand. I am ordering a jib from him for the FX1. He was the sailmaker for Hobie for years and now has been doing some great work with square tops for these boats. Pentex vs Dacron. I would go with Pentex. It won't stretch out as bad but you do have to take care with storing them to get the longest life out of them. Check out www.whirlwindsails.com

Lee Wicklund/Team Chums
N20
Hobie FX1