because there is nobody in the whole world that is riding at a level that a stock hull is holding them back in the surf, in fact aftermarket hulls are holding people back as far as waveriding goes, they just dont turn as good...if u are talking about doing backflips off 6" dribblers than thats a different story..spend your money on something that will actually make u ride better like motor work or tubbies or a properly set up steering/pole/nozzel..
heavier is better in the ocean anyways and thats all you will be accomplishing by switching your topdeck...