i just bought a shell used, put it on the truck and noticed that there is a considerable gap between the shell and the truck on the section that is behind the cab. (below the back windows the width of the truck) the gap is about 1". Am i missing a rubber seal or something? the two bed rails fit well and the tailgate seems good to. I will replace all foam seals as they are wornout but i need more than a new seal for the section in question - missing parts? anyone else with this problem? links for solutions would be great.