Several years ago one of the big glossy mags had an article about a guy who did just that, and added a bulb to the end of the keel to make up for the loss in weight. he did work with a naval architect. If you check www.marsmetal.com
they may have that article on their site. They also can help you with the project, which, as others have said, is not to be taken lightly. Mars advertises quite a bit, too.