If you look at the 2004 nationals report from the US you see we had 37 boats from 15 states ran 10 races over 3 days (three fleets) as well as entire match racing bracket. Considering the winds were less than ideal I doubt anyone could do much better in those conditions.
a fleet of more than 40 boats puts a serious "value" on liquid real estate. As you know a 12 does not manuever like an IOM,
you say 72 boats And down to F fleet....whats that like 15-18 boats per fleet?
If you look at the link for the Champions regatta you will see some interesting things. Of the three "regional" series, the top five skippers are invited to attend, plus the winner of the previous years Champions regatta. 16 boats/skippers all in the top ranks of their home series....and usually their own clubs as well. In my opinion that is more of a Nationals.....however that leaves out the folks that don't have a large 2 day reggata series to qualify...like poor Larry out there in TX.