My 93 Regency has lost most of the rivets and screws that connected the fresh water tank enclosure to the floor of the coach. The enclosure is steel and it appears the underside of the floor is aluminum. Of course the steel screws corroded away and now I have to install bolts through the floor to reattach the thing. It has 20 holes where the screws or rivests used to be on the lip of the steel. Any idea how thick this floor was? I intend to install stainless fender washers and bolts to reattach it. Just looking for how long a bolt to buy.
Thanks,

I was surprised to find 2" foam in the floor above the aluminum, then 3/4 plywood. This was on a 1996 command center.

There is a 5 to 6 square that I found on the passenger side floor over the second polutnion pump ( California specs.) that is alum foam ply and carpet. Who new.