BatteryMinder - to mount or not mount, that is the question.
Are you doing a significant solar install, like the photo you share, or a portable BatteryMinder panel for low power battery maintenance in storage mode?
The downside to a portable is that it can easily acquire legs and walk away.
Rooftop is generally optimum for a fixed installation.
Nice job on that 'window shade' solar panel. I would not have done a solid aluminum backing sheet, however, as he has created a little sealed oven, and heat decreases efficiency and life of the pv panel.
Joe & Joan Donnaway