I also have a 5th wheel and have Reese SS hitch but not a slider. The four "pucks" stick up about 1/4" above bed floor. I use a 1/2" sheet of the closed cell foam board in the bed. The TC just crushes the foam around the pucks and makes a smooth surface for the TC. The TC also settles into the foam a bit too, so there is no movement side to side. I have been using the same sheet of foam for a couple of years now and it hasn't deteriorated much at all.