The 20's remain popular for distance racers... and regions with light winds... (Chesapeake Bay for example) (nothing like a tall mast in light breeze). The F18's have NO foothold on the bay as a racing class.
Very insightful comments, Mark! That explains much of what I've been seeing in the area.
I am currently trying to get back into cat sailing on the Chesapeake Bay. And while I think of myself as a Hobie guy, in terms of competitive small cat sailing, the best option seems to be Nacra 20s and A-Cats with the
WRCRA.