a friend of mine has a flatbed like that.... keep in mind when wheeling any mud or rocks kicked by the tire will get lodged in the bed or penetrate it... the mud she gets all over the back of the cab is nasty
I have a solution...its cheaper and still looks good. Drive up some wheel ramps or other inclined surface. turn hose on and spray at the bed. Everything flows down hill out the tailgate and its clean. I use this and it works great. It also costs nothing and keeps your truck looking good.