4' X 8' X 3/4" sheet of exterior grade plywood. rip it into 4 ea. 2' X 4' pieces on the table saw, then cut a 3/4" wide "slot" at the center of each that is 1' deep to allow 2 pieces to slide into each other to create an 'X' shape. One sheet of plywood will make 2 ea. 'X's', place one under the front and one under the rear of the camper and lower until it rests on the two 'X's'. I place the plywood flat on the bed of the truck before I load the camper.
There are pictures here:
http://forums.goodsamclub.com/index.cfm/fuseaction/thread/tid/23973227/print/true.cfm
Regards,
Jeff