When mine is not in the bed of the truck, I carry it on an over the ladder chair/bike rack like this Over-the-Ladder Chair and Bike Rack - Camco RV 51490 - Bike Racks - Camping World
with it strapped to the ladder with a ratchet strap. Works really well and doesn't cost a lot.
2012 Sandpiper 365SAQ weighing @ 15k, Onan, 2nd air, slide toppers, TST
2013 F350 6.7L Lariat 4x4 CC DRW,Viair 1007, Ride-Rites, Edge CTS, B&W
2001 Chevy 3500CC DRW 4x4, 8.1L, 4.10 gears w/ Detroit TrueTrac
2001 Ford Excursion Limited 4x4 7.3L,V/B Spring Mod, ProComps, Hellwig Swaybar, & other 'Necessities'