The 20 is not a F20 it is a Nacra 20, a one design class with one design sails. Jack and others have told me their concern with making it a 20 is the class cannot survive an arms race. The same happened with the P19 and N6.0.
That's BS. There was no real arms race with the N6.0 and the P19 until they were no longer making class at regatta's
