Catman Mike,
I took out the rivets and I couldn't see anything in the hull that looked like stainless or aluminum backing. I thought about takeing the decks off, but I think that might be too much work for me. I'm thinking about using the zinc fasteners that you use around the house--the type that you push the clip into the wall and screw a long screw into it. That should provide a backing and I would then just have to seal the hole with sealant. I'm just wondering what the effect of zinc would be..