I talked to my PE coworker about it, and he recommended not relying solely on adhesives for mounting the panels. He brought up the Big Dig tunnel Ceiling collapse in 2006, which was due to creep induced by constant loading on the structural epoxies holding everything together, and how that incident caused building code books to remove adhesive as a structural connection until around 2014?ish. He also brought up something I hadn't considered, which is uplift on the panels due to suction from passing trucks, which can induce loads has high as 30 psf, which on a 3'x6' panel is an additional 500 pounds of uplift. Finally, after all that, the most convincing thing he told me was that should the panels fall off and injure or kill someone, I will be found criminally negligent. His recommendation was at the very least to have a few thru-bolts or sheet metal screws in addition to the adhesive, or to forgo the adhesive completely and just rely on mechanical fasteners. I know that anecdotally lots of people have relied on adhesives to hold down their panels, but I'd rather add a few extra holes and be sure that nothing it going to go flying off my roof.
While you said you wanted to minimize penetrations & you actually did the math you need, you might still consider running a leash from your panels to the roof and bolting it in well. Should your panels come up, they won't make it past the back of your vehicle and you will be sure to notice. Lets you trust your theory and still sleep well.
That's an idea I was considering as well, and something that should probably be done no matter the mounting situation. It's a simple, cheap and effective failsafe, even if it does complicate the install a little bit.
