I'm mounting a 14ft aluminum Uhaul moving truck box on top of this M353 3.5-ton military trailer chassis, and I'm wondering whether I should use anything to insulate the aluminum box from the steel framerails. The box will be pretty well-supported and securely bolted down - and the trailer only has a single axle, so I'm not really too concerned about the chassis flexing. But should I use some type of contact barrier? Maybe like a thin sheet of rubber or something? Or can I skip it and just set it down right on top of the framerails?