I highly recommend installing hard panels with at least a 1" airgap.
I have flexible panels mounted directly to the roof and they transmit a ton of heat into the camper. One has already died from overheating. I regret my choices. Just this weekend I was in the mountains and you could feel the heat radiating from the panels. It’s not subtle.
This summer I am going to take these same panels, create a hard frame, and mount them at least 1" off the roof, maybe more.