I would try to mount the rear jack at the back of the camper. You have to have a bracket that will bolt true and inside a vertical 3/4 inch plywood all the way up and down. You also have to support the camper from under. The bracket have to be bent or welded at 90 degree and bolted through plywood to support the camper. They normaly bolt through plywood and a piece of 1/4 inch metal plate. All my campers had this arrangement. You have to support it from under the camper and vertically.
For the front, it is the same principle. Mines where all bolted at front all the way up and down and the bracket bented under the camper. All bolts goes true a 3/4 to 1 inch plywool overlaping the most you can for some good anchor point.
The front is also bent 90 degree verticaly to prevent or limiting the sideways movement.
