Same experience as
@Tex68w &
@Markuson for reliability with my three 4 gallon Rotopax containers. They are stacked, but hanging under my rig in the OEM spare tire location, when used. 12 gallons gives me almost 1/2 tank extra fuel for my '94 Land Cruiser. They are out of the sun and out of the way until needed. They stay cooler and don't swell as much. I fabbed a heat shield for exhaust pipe. Only concern is exposure to puncture during extreme terrain travel, but they're well tucked and are not even visible without getting on your knees. Sure, they're not real convenient to access, but they're only used when needed and much more conveient then being stranded/out of fuel. I also store them in garage between overland trips.