Re: Increasing flotation
"My outboard is a Honda 8HP, so no excess weight there,"
Unless it was designed to carry a lightweight 2-stroke, and you've got a 4-stroke, or similar problem.
Matt, it really sounds like you don't have a clue how displacement and bouyancy work. There's really no way to do what you want to do. It really sounds like you're perceiving a problem that doesn't exist, or a problem that is intrinsic to the design, especially if this is known to be common in these boats.
And if the problem is in the design, it goes back to "see above" regarding displacement and design issues. Get rid of the boat and get one that suits you better, because the alternative will be custom rebuilding your hull.