Personally, I see F18 and A-class as one-design for fleet racing. I know, that's not the correct definition, but if you're racing boat-for-boat without handicapping, that's close enough for me.
AMEN!
BUT, that's not to say I agree that Hobie class regattas should be open to non-Hobie F18s. That has more to do with the support and purpose of the HCA and HCC.
I never really understood that, but it's your game so more power to you.