Proper campershell alignment help!

Bought a used campershell a year ago or so and love it. Issue is I can not get it to sit properly aligned on both bed rails. The passenger side always extends past the bed and out a bit when I get the driver side aligned correctly. I never had a campershell so it’s all new to me. I’m assuming the campershell outer edge should run in a straight line with the bed of the truck. Even if I try to let it flare out as it goes back the other side is still way off. My truck is a prior salvage so things. A slightly out of wack but I can’t find any measurements off with the bed of the truck or with the campershell. I can not figure out why it won’t sit in good alignment with the bed. Any tips or tricks anyone has to help me? Thanks!

 

If the out of alignment is at the back..... have someone get inside while you close the topper door and push the out of alignment side in where it should be. When it is aligned have buddy tighten down the topper clamps.