You can locate the panel mounts in such a way that the "Holes" are under the solar panel once they are installed.
By using 6" long 2X 2 aluminum angle, you can make a mount with 12 square inches of surface area, and with rubber roof sealant, it is tacky and will hold the panel in place, and also seals the screws so no water can get past the screws.
The RV will use about 35 amp hours per day just to run the CO and propane detectors as well as the refrigerator. That is about how much power one of my 120 watt panels can make in one day.
You might want to check panel prices here.
SunElec.comFred.
