It'll take a few custom motor mounts, but I bet the area just above the back wheel would work for it, the second bar parallel to the ground.. the tank should mount directly above on the next bar, just ahead of where the chain passes. Of course, anything you tried to take in your pockets would be shaken out of them. (edit: Looks like there's something trailing down under his left arm and along the ground from somewhere above already)
That reversed trike layout would provide some nice stability though.
When I worked at Poly I caught part of the engineering students bicycle contest, one year.
Some of them were WILD !
The one I recall is where the student was riding it in the position of a swan dive... it was un-believable! but it worked!!!
Another one I liked was the Japanese students do some kinda art-form architectural project where they fab a design from cut up one of those acrylic lawn chairs for the components... Some really interesting stuff, for sure!
Cal Poly is where they did the first ever Tractor Pull contest.