I was actually thinking of using a section of an aluminum extension ladder for the base below the plywood floor, and probably something like 1.5 inch square aluminum tube for the rest since it
would only be bearing the weight of the empty trailer itself during the ride, and would take no strain when the trailer was being used for sleep, because it would have the wheels removed and
would sit flat on the ground. I don't know much about the strength of the 2 metals though, does that sound like it would be strong enough?