During my search for a trailer, I looked at many older units. Common to almost all of them, the main propane
supply line was iron pipe, running down the middle of the underside of the trailer. There were 1/2" copper tubing take-offs from this center pipe to the individual gas units (furnace, water heater, stove, refrigerator). In all cases, the tubing showed rock damage, in some cases, almost squashed flat!
In my Fiber Stream
, the previous renovation used short pieces of split garden hose to protect the copper lines at the floor penetrations. I simply took this one step further, and covered the complete tubing runs in split garden hose. I ended near the gas unit, but well away from potential heating issues. I also found that if you use the cheaper garden hose, it tends to spiral when split, making it easier to cover tubing bens completely by spiraling around the tube.