You will have to install a roof vent and side wall air intake for the frig to work at all. Failure to do this and the heat buildup behind the frig will cause it to fail if not a fire.
Do Not attempt to run propane through a Hose under the trailer road rocks nay strick it a cut it while going down the road. That would make for a fun trip.
Propane should be piped directly to any gas appliance and as much of the piping out side the living space under the trailer. When piping use black iron pipe or flared compression fittings on the copper piping.
This is not an area for a Rube Goldberg approach.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles