One thing to remember is that wind speed is not road speed. We hit 40+ MPH head winds for days it seemed like two years ago when we went to California. Add that to vehicle speed of 65 to 70 plus wind gusts from passing semis going the other direction...
We have a single 66 cell high voltage panel (big) that has six ABS plastic mounts held on with 3M VHB tape to a Filon roof. I did this after calling #M and talking to an engineer who told me how much contact area I needed and the surface prep necessary. If I were to do it again I might use 2X2" aluminum angle. You do NOT want to completely enclose the bottom of the panel to allow for cooling.
