Okay. Researching ways to mount a Rotopax and I was linked to this thread. A bit of fail in the above that needs to be corrected. 5 gallons of "gas" weighs LESS than 35lbs, it does not get anywhere near 50lbs (so almost 1/3 less). The weight of gas varies because of density due to temperature, but you are looking at between 5.8lbs to 6.4lbs per gallon of gas in most normal temperature ranges. So, 2 x 2gal Rotopaxes will weigh 8lbs (4lbs each dry) and the fuel will weigh right at 24lbs. So 32lbs total on the HF hitch as the guy on the first page showed. Most bikes (not talking what a "roadie" would use...yes, they get under 20lbs easily), weigh in the vicinity of 30lbs a piece. So, yes, that crappy little Harbor Freight carrier is well within weight spec. Put an "anti-rattle" device where the hitch / receiver meet up and you have near zero side to side play. Same for any other receiver / application too.
As for never mounting fuel at impact height, 90% of rear mounts--tire carrier or otherwise fit this. So, either put it on top or on the side? How about you don't drive around with fuel in those containers until you are about to go off pavement, fill them up, emptying them out when the gauge shows your low enough, and call it a day?
Don't know if I'll use it, but I like the common sense creativity on the first page of this thread.