I've owned a Supercat 20, 12ft beam and a nacra 18sq, 11 ft beam. I'm a bigger guy than the f-18 skippers usually are and I think a wider beam (12') 20 foot cat is a great platform. I just saw the 2nd Nacra 20 Carbon to come to the US up close this past weekend and I think a box rule that is a maximum (less than max ok) is a good idea, with a simple list of rules like the a-cat it will foster development.