Solar panels mounted on truck Tonneau cover?

You could use something like Adjustable Solar Panel Mount Mounting Rack Bracket along with the Renogy mounts. Mount the Renogy mounts on the tonneau cover and the adjustable mounts to the Renogy mounts. That is what I did for the top of my TT. The adjustable mounts can also help maximize the sun angle too. When you aren't using the solar panels, they will easily come off with the adjustable mounts, leaving the Renogy mounts still attached to your tonneau cover. You could also use those adjustable mounts and sit them on the ground, still hooked up producing energy.