Brettski, I am by far an expert on Geo systems and can only speak from my limited experience on my own. I recommend getting as much info as you can from an insaller and or manufacturer. For planning purposes I can give you a few tidbits I picked up that may benifit you. Putting the loop in before the pond fills is a good idea because a trench had to be dug to mine after it was filled resulting in a spot that has been difficult to smooth out and a steep hole where they didn't fill it back in enough just below the water surface. My installer said that the inlet/outlet pipes need to be a certain distance apart and not cross water lines if possible because the ground will freeze deeper where the geo is sucking heat out of the ground. Will the mat float? I'm not sure. I would contact installers and leave it up to the pros. I'm a big doityourselfer, but I believe repairs/replacement later would be expensive if not done correctly.
"The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge." Stephen W. Hawking
