Why don't you ask the harken organizors this question.

What happens when a Hobie Tiger sailor shows up with big sails and insists on sailing at 308 as a Hobie Tiger one design.... Do they include him in as an F18 for their series?

The answer should be... NO, the class is NAF18 and the rule is. xxx (see where ever they post their class rule) and NO you don't measure in so you can't be scored as an F18.

The sailors agreed that the class will be NAF18 and they will use the published NAF18 rule set... Nobody else should have much to say about your class rules.

Classes in the US Sailing structure are self regulated or regulated by the builders. The fact that a portsmouth rating is assigned to all of the configurations that you could sail the boat is just a matter of convience for the PRO and scorekeeper and the sailor... It's and easy way to tag the boat configuration... for example Nacra 6.o with NE spin. or Hobie FX1 two up and no spinaker (its a racing class of one boat in the USA... 4 more like Steve B and he also has a class)

Another example, The Dart 18 class rules used to state that the Sloop and Uni are part of the same class and can be scored as one class. Indeed the Canadian Dart Association conducts their nationals this way. (Mind you... IT DOES NOT HAVE TO BE TRUE FOR IT TO BE A VALID CLASS) Years ago, the Hobie 18 Magnum and the Hobie 18 were viewed as seperate classes even though they never proved to differ in performance. My point is a class is a social construct and if everyone involved agrees on the definition... so be it.

If you can point to your published rule set... then it should not an issue for the Harken series... Hell you could require a naked hula girl on every spin pole to be a class member and they shouldn't have any complaints. Those who refuse... don't belong to your class... they are classless (grin)!

Mark