I'm presently using a 3/4" foamboard topped by a heavy rubber mat under the camper. This raises the camper by about an inch. Measured the cabover clearance above the top of the closest running light and it is a little over 4". I've not heard there was a change in cab height of the Ram and the new Bigfoot manufacturer is using the same fiberglass molds used when my 2008 was made so you should be good even without anything. But I highly recommend using at least a durable rubber bed mat. The manufacturer cuts openings in the bottom of the camper during construction and affixes them back with screws. Judging by the wear marks on my rubber mat my Line-X bedliner wouldn't have been enough to protect the bed alone. I added the foamboard after I had a gooseneck hitch installed as the chain ties stick up just a bit. Would probably be fine without it but it also makes it easier to work the front electric hookup.
