You would know better than I if the benches are structural or just clip on, and looking closer I would agree that they need a reinforcing bar somehow to actually be able to use the buoyancy of those floats. But if he's using them only for when he gets a little off balance to prevent a full-blown capsize they may hold. I wouldn't patent something with a "may hold" level of certainty, though. BTW, can u lift a 17 by the wings, a person lifting on either side?