Rigid Solar Panels on 1/8 Luan Roof

I make no claims of expertise in this matter, but I'd suggest that there must be framing members at the corners at the very least. I think I'd look into bolting rails to those framing members, and then bolting the panels to the rails. This would also give you the option to change panels, or their orientation and number without extra holes in that roof. I also bet there are framing members spaced across the roof. I'd look for those. The luan/foam/ceiling panel you describe would not be strong enough on its own, with no framing members, to span 8 feet by 16 feet.

To be sure, you need to make sure they stay put while driving into a strong headwind at 70 mph. The paperwork from taking out the windshield on the car behind you would not be fun.