Most things in the upper cabinets will be all over the floor unless you do some serious work to keep the doors shut and the loads inside the cabinets in non slip bins.
The possibility of hooking a camper leg or getting towed with the load on is scary enough. I do not know whether you could be towed backwards with the camper on. I don't think you can get past the Suburu's anymore.
My Snowbird was a slide 9'6 and I did not feel happy taking it off the beaten path very far at all.
At a minimum I would put a wooden frame from camper sides and front to the sides and front of the box to hold it in place from slipping forward or sideways. Both front and back spring loaded tie downs should pull the unit forward, and the wooden frame in the front should hold the bottom of the camper away from the rim of the pickup box by a couple of inches.
