What he said, also 20x20 is an odd size for a solar panel, what sort are you considering, and it would probably be helpful if you share your location and pool information if we are to give any other beneficial advice.
Ike
p.s. Also that is a LOT of weight, the panels I have only have a wet weight density of 1.31 psi (or 64 pounds per 4x12 panel) These are Techno Solis brand panels which weigh considerably more than most brands do, for comparison some Aqua Therm 4x12's panels have a wet weight of only 48 pounds or 1.0 psi wet weight density.