I'm no expert, but I believe you can make a splash from an existing boat by coating the hull and fiberglassing, then use that fiberglass shell as a mold.
A design can be protected with patent, but I think all a copier has to do is change the shape by a certain percent to qualify as a new design. And since the top is easier to change without R&D...most just do that.
As far as copying going on...because it's tough to fight the legal battles, it'll probably continue.
jer