I used to work with a guy that did the same thing years ago.  If the boat does not have to be seen to get it registered, tell them it is a homemade boat.  Then, go home and make something to mount on the front of it.  Use your imagination.  I mounted antler rod holders on one for a guy I used to work with, and believe me, it made that boat.  Anyway, every law has a loophole.  You get your numbers, you made something on the boat.  Its all nice and legal.