Well, in the United States I have never heard of a class asking for permission to hold a National Championship. I am absolutely positive that it is not required. (I can't speak for ISAF Classes, but it is definitely not required for non-ISAF Classes.)
We have been holding the Wave National Championship for many years, and we hosted the first and only F16 National Championship (only five or six boats at it ).
The only reason I asked whether there was a minimum number of boats required for an F16 Nationals was that I thought maybe the class itself has put in some sort of rule about that.
So why not have the 2nd F16 Nationals at Gulfport?