I get roughly 23.8 lbs of liquid (6.8 lbs/gal for most liquid fuels), so guessing about 25-26 lbs for the fuel and the can. Really, really rough Rule of Thumb for Dynamic Loadings is 3 times the static weight, so around about 77 lbs swinging up and down and fore to aft and back on every bump. My NATO cans measure 13" wide by 6.375" deep, so that puts the centroid of the weight (mass actually), in the horizontal plane, ~14.5" from any corner.
That makes the Moment on the jack bracket something like: 77 lbs X 14.5" = 93 lbs-ft (can think of a Moment as a torque). What this means is that every bump that equals or exceeds 3 times the pull of Gravity is exerting at least 93 lbs-ft of torque on the jack bracket. This doesn't include any Impulse loading from the can not being completely full. That can drive the actual, extremely brief duration loading significantly higher (think: like hitting the end of that 14.5" long lever with a 3.5 lbs or less hammer).
Because I know all of this I know it would fail for me. It is the curse of an Engineering education. Hopefully my outlining it all doesn't mean it will fail for you too.
EDIT: DOH! moment (no pun intended). I calc'd the diagonal of the whole can, not the centroid location. I kept looking at that number thinking it was too big. So, the actual leverage length is roughly 7.25" which makes the Moment 46.5 lbs-ft instead of 93 lbs-ft. Still quite a large number, but it will increase the fatigue life over the 93 lbs-ft number.