Steve,

We do that at smaller local regattas. With my 6.0NA (no spinnaker) it's rating was very similar to the F18s. if I were one of one or two open boats I was put in and scored with them on a couple of occasions (would do really well in light air and not so well in heavy air). Our race committies are usually very open to doing this when both the ratings are similar and the sailors agree.

As far as the F18 rules excluding older designs, it's a "damned if you do, damned if you don't" thing. In the case of an F18 organziation that is trying to appeal to the broadest audience possible, there is a very fine line between having a rule set that makes it fair for all manufacturers to compete and a rule set that allows too much unrestricted development making competition very expensive and turbulent. F18 has done a very good job establishing a rule set that is strict enough to allow fair competition but keep the costs low. If the rules begin to broaden to include other older designs, the risk is that some other areas would be opened to development. Even then, what boats would want to be able to adapt to the rule? The Hobie 18, while is a great design in many aspects, doesn't have the high aspect boards or latest hull shape (advantage?) or the proper mast height, etc. The Inter 18 fits most of the bill but has a carbon fiber mast. First) do these sailors even want to be part of the rule and Second) will opening up the rules to include them inadvertantly create unstability in the class?