I was thinking of BoeShield (http://boeshield.com/) for inside the frame after letting my air compressor have at it for a while so it'll be dry. I have a buddy, who's an aerospace engineer at Boeing, but hasn't heard of it. I asked him to ask around at work to see if it would be the right stuff. Was thinking of using a nylon 12ga bore cleaner to get it as clean as I can before the first application.
As for the pontoons, I'm gonna try TheAsianGuy's suggestion and go with the Aerospace 303 protectant. I see a lot of salt residue built up on them even after a half day on the water. He has done some tests that makes me want to try the product.
Fellow pontooners, what do you do to protect from frame corrosion?