I would recommend a permanent solar panel. You can buy a 140 watt 12 volt panel at this place for about $229.
SunElec.comYou can make brackets out of 2" angle aluminum - cut 6" long with 3 holes for #10 screws into the roof and 5/16" hole for a 1/4" bolt into the panel frame. Make sure that you buy solar panels with frames, not the lower cost frameless home style solar panels, designed to fit on frames bolted to the roof.
I also think that you can get much more bang for your buck with a PWM controller. It is to low cost to buy more panels, and install the cheap $20 20 amp PWM controllers.
I have a SB50 amp MPPT controller, I think that I paid about $400 for it back in 1999. Now it would be much less expensive to just buy an additional panel, and make up for the power that way, not buying a expensive MPPT controller.
Good luck,
Fred.
