lol at your sig.Bolt your box right down to the chassis, my friend did it and it was killer.
Or try plummers tape.
velcro, tie down straps, thru-bolts on the box, fill the other area around the back of your vehicle with crap so theres no room to move, disgusting amount of duct tape...they were thin.. they dont look very heavy duty type so. but i am going to go to home depot and get me some big *** head duty ones!. any other recommendation?>