OP here. Grit dog is right and the question was me trying to get my ducks in a row before I made holes in my roof. I never had any intention of attaching the panels with any adhesive/glue/tape.
Anyway, I finally got around to mounting my panels. I called Host a few weeks ago to ask where to find the the rafters and was told they attach the factory mounted panels to the frame at the outer edge of the camper and then the inner brackets they just screw into the 1/4" marine grade plywood under the rubber roof.
I'm almost done with my electrical upgrades and will post about the finished product in a few more weeks.