Actually, at the very beginning, the North American rule had a different weight than the International F18 class - I don't recall if it was heavier or lighter (I think the NA rule was actually lighter than the F18 standard). However, that weight discrepancy between the North American and F18 rule wasn't in place very long. The same folks that ran the Nacra classes were heavily involved with the formation of NAF18 organization at the outset. A year or two later the NAF18 class fully adopted the European rules.

The Tigers at the time (which I think Tom is getting at) were in the US in force racing mostly Hobie one design and we all quickly came together to race F18.