Camper shell Over A Bed Liner

I got a new camper shell for pretty cheap and the only problem I have with it is that my bedliner seem to interfere with it... I don't think it is pushed all the way forward and I will have to cut holes in it to use clamps. The guys who owned it before me just had some bolts running through the bed and the topper. You can see the holes in the pictures. Does anyone have one of these on their truck with a bedliner? If I cut the front lip off the bedliner the topper should slide all the way forward. I'm just worried that I am going to ruin my bedliner and its gonna sag or something.

 

You can't put a rubber seal inbetween and clamp it down?

 

Drill 2"or 2.5" holes in bedliner ,below the metal sides of the bed- 6"-8" back from the ends of the bed- Two on each side of bed & use 4 camper shell clamps OR 4 c-clamps to hold it on