yes! Keep it clean AND keep those pesky dogs off it, I had to repair mine this spring, didn't use the typical plug it method, just "welded" it with some of the same plastic so i could keep teh trace working and not lose efficiency.

Poconos - wrt your field system, I understand why you have the black under it, but with the mats you would get a slight negative effect.
have you ever tried reflective under the field system? I'd be interested to see if it improves - it probably would because instead of the underneath absorbing heat, it would reflect it back onto even the undersides of the pipes.

You can get thermal blankets at camping stores that are reflective plastic sheets big enough to wrap a person up - very thin, but very effective and cheap - they'd work.