I don't know whether he is a member of MASF or not, but that would be irrelevant for putting boats in classes for the race.

I think the boats racing as "MASF" are boats that have a rating issued by MASF, whereas the RC-27 and RC-30 have Portsmouth numbers.

The Stiletto 23 has a Portsmouth rating, but apparently it also has a MASF rating (and that must be the one he chose to put on his registration form), since he was in the MASF class.

One of the interesting features of the Miami-Key Largo Race has always been that you don't necessarily know what class you have been put into and who you are racing against until it is all over and trophies have been awarded and results have been handed out. All you know is that you are trying to get to Key Largo as fast as you can (by sail and on the water).