Mounting 165 watt solar panels

I'm looking to install my panels this weekend and I'm a little oncerned about how to mount them securely. My 5th wheel is a 1996 Coachmen with what seems like a tin or aluminum roof. I've purchased z brackets from Windy Nation, 6 per panel. Now I realize they only take 1 screw per mount into the roof. Not sure what type of screw to use, nor whether these mounts are even the right ones to use. Anyone have any thoughts or suggestions.