Somehow the idea of carrying a container with explosive liquid sloshing around with fumes high up on a bike just seems wrong. I would never do it...think about static electricity generation, an insulated plastic container in a fiberglass / plastic abs insulated shell...sounds like the makings of a bomb to me!
BTW my TomTom can be set to alert if there is a gas station nearby, so I just would not take the chance. There are plenty of laws on the books about transporting flammable liquids like gas and propane in special certified metal tanks, think boating here, they do not certify plastic tanks last time I checked (in the early 80's anyway). A couple dollar plastic container with electronically welded seams with a handle just does not sound good to me. I know the endurance Paris to Dakar Adventure Type riders carry metal ones, BUT...