I don't have any experence doing what your doing, but what about putting the vent line up in the bed stake pocket? It would be out of site and 18" up...don't forget the roll over valve.
Mike B
Mike Boteler
1956 Chevy 3100 Resto Rod 1952 Willys M38 Army Jeep 1983 Jeep CJ7 Laredo 1984 Jeep CJ7 +++++ Silver Spring, MD