Hi,
I would recommend a 300 - 400 watt solar system. I had 400 W and still needed to run the generator a little bit when I was spending to much time watching TV. I would also recommend smaller 100 - 150 watt solar panels, and 12 volts is what I am running - mainly because that is what was sold back in the 90's.
Larger panels are to difficult to find a good place to locate them, and might offer more uplift than the 4 brackets would handle.
I placed my brackets in such a way that the screw holes ended up under the panel once it was mounted. I used "Nutserts" to make sure they stayed there, along with tamer resistant 1/4-20 bolts 1" long. 6" long aluminum angle from Home Depot with 3 holes 3/16" in one side to the roof via rubber roof sealant and 3#10 screws, and 5/16" hole for the bolt into the panel frame.
SunElec.com offers great prices on solar panels.
Fred.