Thanks for the explanation, Richard.
Do you use a solar cover at night, too, to hold in heat? I find it's critical to efficiency.
If you have an attic, have you thought of running additional plumbing through THAT to pick up more heat energy?

Luckily, since my panels are only about 3 1/2' above my pump and, at most 10' away, I don't have to deal with all those issues you do.