Reading this good info has given me inspiration to do a similar project. I just ordered a 20' piece of 316l, 3/4", .065 wall stainless and I intend to make a "spring- like- coil" in my Alaskan. I am going to stray slightly and utilize the coil in a closed loop radiant heat system. I have 3 zones already plumbed with tubing that are resisting connection to the fuel oil boiler. I will keep you posted.