Yeah, same here, the kit car community started using bedliner as an undercoater for fiberglass years ago. The older Cobra kits didn't have the thickest glass work to begin with so as stones got thrown up in those big fenders they would "star" through the gel coats and paint work. With nice thick bedliner app. the stones just bounce off.....

I'm not sure if this would be as desirable as the typical bedliner, but I used something on my trailer floor that is tough, and built up pretty good. It had non slip stuff in it and it holds up well even with hot slicks on it. It is a product made by Kelly Coatings called Convoy II. It may be a little more economical that the Upol. I used the Upol in the trunk of the TA mixed with some basecoat to match the car and I'm planning to do the rear wheel wells with it tinted black. It goes on pretty nice with a thick roller too it you don't care to by the gun.
JT