Timbo,

The 2004 Portsmouth numbers are on the USSA website (I think Rick has a link to it). The F16 is rated significantly slower than the F18. Wouter claims to have designed the class to be as fast as the F18, which would mean that the F16 and F16 Uni (rated even slower) have attractive Portsmouth numbers for Open class racing.

It is the Race Organizer or Race Committee that will decide if you get to start with and race with the F18s, but it never hurts to ask. Best of luck.