Hi Phil,
Thanks for feedback on the Hobie 18. Just from Gary`s post it appears that a well-sailed one is not far off his pace upwind, and his pace is not far off Hobie Tiger`s, but all things considered the sailors would all have to be identical in skill before any conclusion can be drawn. If you could add a kite to the TheMightyHobie18 that works for that boat it would be faster than it is. Doesn`t have to be full-F18 spec, could be smaller if the bows won`t hold up full F18 sail areas. Would make a cheap way to go Formula sailing, but I`m sure the F18 class wouldn`t allow it, I`m sure the TheMightyHobie18 jib is oversize in their class rules. (And Hobie dealers would panic - Imagine all those cheap used TheMightyHobie18`s being resurrected to F18 specs, would dent their sales figures a bit ) MAybe that`s why a dealer told you it won`t hold up.

Back to Gary, since he hasn`t given you an answer yet, I think he used the A-class rating based on the fact that, on ISAf / Texel, F16 solo is rated equal or very close to A-class, while F16 sloop is rated equal to F18. So it`s easy to convert that to any handicapping system you might be using, use it as a benchmark until you have some results and correct it out if needs be after a few regattas.
I think there is a little resisitance from US sailors to have their F16`s rated equal to F18, they are enjoying a rating that allows them to win, why should they want it to change !

Steve