I have direct experience. I put the new Bigfoot in the old truck which had always had a drop in bed liner (Duraliner). It slid around in cross winds and bumpy roads. Following the advice on this forum, I removed the Duraliner and had Line-X sprayed in. The camper moved around just as much on the Line-X as it had on the Duraliner. Same truck, same camper, same roads. When I replaced the truck, I put in a new Duraliner.
My solution was to put in a plywood platform on top of the Duraliner, with a thin (3/8") rubber mat on top of that (to protect the plywood). The plywood fits the bed and will not move, and has low cleats down the side to prevent the camper from moving. This has solved the problem.
A drop in liner will protect the bed far better than Line-X. When I removed it to do the Line-X, the 11 year old bed looked factory new. After the Line-X, it picked up a few dents. Line-X is hard to scratch, but easy to dent.
A drop in liner will sand the paint where it touches and moves/vibrates. This can be effectively stopped by putting down a liner liner before the Duraliner. This is a sheet of 1/8" PE foam, sold for this purpose or sourced elsewhere.
The Duraliner will hold water, I consider that a plus, but if the truck is parked with the bed sloping forward and you get a hard rain, it can collect water. If parked with the bed sloping aft this drains down the grooves. In addition, the grooves allow it to dry underneath, which was not true with the Line-X, it would stay wet for weeks. If you want your Duraliner to drained when parked on a slope, you can drill holes in it - then it drains like the holes in the steel bed. But I wouldn't.
