Thanks for the info, guys. Actually, I already have my new tubing
running ACROSS the floor for now so that we have hot water in the
meantime, so I don't wanna have to buy more tubing that comes with the
cover. Also, the channel isn't a straight line - so rigid PVC isn't
really an option.

I probably can just get some type of plastic tubing/hose of the proper
diameter and slip it over the copper before I cover it w/ concrete. The
20-year-old kid who works in the Plumbing/HVAC aisles at my local Home
Depot actually is quite knowledgeable, so I guess I can just ask him
what type would work for me.

Thanks again!
JohnB