I use a rubber mat in my dually to haul my 1161. The camper is very stable and does not move. Fully concur with your dealer: get rid of the plastic liner! Too slippery to be hauling the camper on and probably adds a coulple of inches to the height of the truck bed floor. I don't have the bed sprayed yet, but you bet it will be Linex when I do! Everything I read is good stuff. Multi-color and fade resistant depending on the dealer/installer capability. Shop around, ask lots of questions, and make your best decision. Lots of post here on the TDR about bed liners; Linex and other brands. Do a search. You'll be glad you did!
BF