If I was me, I would visit
https://lifestylepropane.com/...or similar.
.
I would hire them to fabricate a legit propane system.
I would go into the fabrication shop with the technician, and I would watch-n-learn as they build my system.
.
But a custom job may not be necessary.
In the
https://lifestylepropane.com...showroom, they stock dozens of sizes of dozens of types of flexible hose.
.
I have no way to prove it, but I think -- in a vehicle -- copper will eventually fracture at the couplers.
Hence, my decision to go with flexible hose.
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An aside:
For the reasons you express, we engineered our ExpeditionVehicle with standard COTS (Commercial Off-The-Shelf) camping equipment, including twenty-pound five-gallon propane bottles.
We use easy-to-use easy-to-find easy-to-replace manufactured rubber hose -- Coleman, Mr. Buddy, Ozark Trail, etcetera -- available at most hardware stores.
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An aside:
We always park and travel with the valves 'CLOSED' on the propane bottles.
.
Cooking:
Nearing the end of our fixing a hot meal, we 'CLOSE' the valve on the propane bottle.
We finish cooking using the gas inside the hose.
We can usually time it for the end of cooking at about the time the burner sputters out.
.
Heating:
We use our Use-The-Gas-In-The-Hose® system with our Wave 3 catalytic heater.
Nearing the time we would shut it 'OFF', we 'CLOSE' the valve on the propane bottle, and allow the heater to gradually burn out.
