My chief concern with copper cables would be that copper is quite malleable, and might stretch and/or have insufficient tensile strength in the moment when it was needed. Steel cables would hold firmly, and if strung from one eave, over the ridge, and down to the opposite eave (which is what I was imagining when I suggested them), I think it should hold well enough, provided it was suitably attached to the panel's base, and provided each end of the cable was well anchored, not just screwed to the external fascia board. Mathematically, you would be holding from two different vectors, and if the cable were tight, there should not be much wiggle room.
Running a plank on either side of the bases with multiple attach points on each one (at least two, if using sturdy lag bolts, more if resorting to deck screws) to prevent the bases from even flipping over would be another way of sturdifying the assembly, and again, without needing to puncture the roofing and risk leakage. The cables would still be necessary to hold the assembly down, but this would greatly restrict movement and by tying it all together, the weight would be increased in order to budge even one part of it (all or none). Of course, winds are more powerful than many understand, and with the panels' exposure, the potential force is substantial. (If I've done the math correctly, with a conservative estimate of each solar panel being about two feet by three feet in dimension, i.e. 6 sq. ft. total, each panel would have a force of around 55 pounds of wind load in a 60 mph wind. But increase the wind to 80 mph and the wind load is nearly 100 pounds per panel. With the angle of the panels, some of that will be a lifting force, like for an airplane wing--which would reduce the resistance to movement based on traction with the roof shingles. Lots of physics to consider.)
One thing's for sure: I would not fancy carrying a piece of plywood (okay, 32 sq. ft. of surface area) on that roof with even a 15 mph breeze! I think I'd be a nose-diving kite!
. They weigh 42lb a pop plus the 2x4 structure so a solid 50+lb per set. I will add an eye loop at the bottom of each and run a long fake rock climbing rope (the ones you find at home depot for 20/100' and are 1/2" diameter.... I will connect to the bottom of each triangle structure and anchor on the side of the house at each end. If things go really bad (i.e. hurricane winds), then the tripod might topple on the roof but no 50lb panel will go flying off the roof.
