Update! Installed a aluminum roof skin.
We ended up buying a 21 foot long 103" wide coil of 0.040 aluminum, hoisted it up on the camper roof using some pulleys fastened to the house roof joists, and unrolled it using my wife's clever idea of c-clamps right after the leading edge of the coil. Every 340 degrees of unrolling we would move the c-clamps to a new position and this kept the coil from uncontrolled expansion. Worked so easy!
We first put down a layer of Tyvek on the plywood roof...more to act as a barrier for anything in the plywood that might attack the aluminum...although the plywood is only exterior marine grade and not pressure treated. The interior of the camper has a full moisture barrier on the warm side consisting of aluminum foiled 2 inch polyisocyanurate insulation with all seams sealed with aluminum tape.
We only bonded the aluminum for about 2 inches on the top around the edges with Sikaflex 252 (aluminum to plywood bond). After that dried for a week, we bent down the edges of the aluminum and Sikaflex 252 bonded it to the aluminum sides, along with some screws (with rubber washers). The top flat part of the roof has zero holes. The curved part I sectioned with a jig saw into 1.5" cuts and then bent them down and Sika'd them along with an insane number of screws...which actually looks kind of cool. The bend is very smooth.
When all cures, we are going to coat the roof and side flange/screws of the roof with 2 part spray raptor coat to give it a little bit of protection and improve traction and appearance.
I am quite pleased with our roof...probably good for 20+ years.
