We had an 11.5' Lance camper on a F-350 for 10 years. Bought the truck & camper as a Bundle, but I specked it to have a sprayed on Rhino Liner done, and a 1" thick rubber mat under the camper, a Camper Tie down system w/cab over stabilizers, prior to purchase/delivery.
For Licensing purposes, we left the camper On the 350 for the whole 10 years.
When we sold the Lance and bought a FW, and I removed the camper, the Mat had taken the shape of the Bed (with liner) contours. Both looked Factory New.
Sooo.. YES to a Spayed On Bed Liner, and YES to a Bed Mat.. between the two ?
A Plastic Bed Liner ? NO WAY.. I've seen too many of'm Broken, Cracked and/or laying along the Highway ditches & shoulders.
On the other hand.. I've seen bare truck beds After a camper has been removed.. Dirt, Grit, and RUSTED metal damage prevailed. Not Good.