There was talk of a Rib forerunner in / around Plymouth at the same time Atlantic college was working on there's.
Story was that it was an inflatable that got its hull ripped out and some one put a plywood hull of some description. What ever happened to it no one seems to know.
It looks like nothing more was done on the subject, so the main players deserve the credit for developing the idea.
It could also be a sailing club bar story, without further evidence we'll never know!