Good to be concerned with a fiberglass roof, temperatures from undersides' radiation can get super hot.
Air circulation when stationary is critical.
Stopping the panels blowing off comes from the strength of the panel framing rack and its connection to the surface below. Do NOT use the "semi-flex" type, but fully framed glass covered type designed for professional home installs, high voltage and rated for hurricanes.
To reduce lost mpg all that's needed is a front airfoil.
I have seen an "edge lip" all round to make panels less visible basically the panel space is "sunk" into what looks like a shallow pool space.
But that would impede air circulation and be difficult to DIY.
My reco would be using thick layers of very strong and reflective waterproof coating to protect the fiberglass itself, pretend you will be under constant attack by aliens blasting infrared ray guns.
Then thick thermal insulation underside to keep the heat out, maybe even a professional spray foam job.
If you can, attach a strong roof rack to the vertical steel bits, top of the load-bearing posts?
to hold the framed panels at least 2-3" above the roof surface
altogether weighing maybe many hundreds of pounds that may be the biggest challenge.
Or, second choice by far, just use the bare frames with 2-3" spacing brackets, PlusNut'ed to the fiberglass itself.