Anyone will be able to submit their boat even if it doesn't meet the spec. ISAF will then do a paper evaluation and invite selected boats to the trial. It doesn't mean that even these shortlisted boats have to adhere to all the requirements in the spec, however, I'm sure there are a few show stoppers and some "nice to haves".

For example, it says Sloop Rig, but if someone can come up with a good arguement why a cat rigged boat with a spinnaker would work, then I'm sure it would be in the mix.

And I can't speak for Hobie Cat, but I would be surprised if they even put forward the Hobie 16.