Plus 1 for DualLiner. Although it's not perfect, I
much prefer it to a spay-in liner or a drop in. I've tried both, and the DualLiner has 'em beat. I had our camper loaded for weeks over the Winter, we've gone about 7,000 miles loaded, and there are no indications on the mat that the camper was there.
It does a good job of keeping stuff out from under the mat, but there's a little that gets past. This is my DualLiner (installed when the truck was 3 days old) after 9 months of every day use, before we bought our TC. I haul mowers, bales of straw, bagged mulch, construction debris, etc. A lot of material that can blow around. I think it looks pretty good for the use it receives.
This is how much material passed the interface of the side panels and mat. Again, not too bad. This is the first time I had lifted the mat and removed the side panels (after 9 months).
Other than a quarter-sized rub spot on a fender well, this is the only down-side to the system I've encountered. The front panel piece curves and scratches the top of the bed's front rail.
The panel installs with the mat riding over a bottom lip of the panel (which sits on the truck's bed). The panel was installed correctly, but there's too much slop in the height of the panel, allowing it to flex and scratch. My solution was some angle aluminum, a roll of self-stick foam, and some stainless steel acorn nuts/hardware. The foam tape was applied to the top and face of the truck's top rail. The holes in the angle aluminum were counter-sunk for the screw heads. Lock washers and blue Threadloc assure everything stays put.
I know the scratches are there, but I don't have to look at them. No more curved front panel, either. I have yet to encounter a situation where the acorn nuts interfere with a load. All things considered, I'd definitely get another DualLiner. Their customer service is outstanding, too.