Don't know anyone that has one of their 17 square tops, but have heard nothing but good things about them. Chuck used to make sails for Hobie, and is supposed to be very good! I wouldn't hesitate to order from him if I was looking for a sail for a cat. I think a couple of the guys on the Yahoo beachcats group put Whirlwind squaretops on their 18s, and love them.