Welcome to the F16 Forum "contender",
I have started new post to reply to you as I think welcome post is not meant for replies?
Anyway, to answer your question I don't know of anything that would stop a Hydra or Cobra from being compliant as standard. If you put different Rig or Sails on it would be just a matter of getting them made within the rules.
That is one of the concepts of the F16 class to be inclusive of as many existing designs as possible.
I assume you are in OZ somewhere what state?
Does your nickname "Contender " refer to having sailed one? You mentioned you have sailed high performance dinghies, I grew up sailing Fireballs and sailed Contenders for most of the 90's. But now F16 gives me everything I want, it is like being a born again sailor.
If you need any more info just ask. It's not that long ago as a Mossie sailor I was doing the same thing.
Regards Gary.