I had a buddy that cut and sewed carpet to fit the sides and floor. The sides and bed were one piece and the front was a separate piece to keep the number of seams down. He used a lot of magnets to keep the carpet on the sides, something like 8 per side and 6 on the front. Trying to remember if he used any on the floor. I don't think so. They were strong enough to keep the carpet in place and it didn't shift but they didn't damage the paint.
