Stian, This is a serious problem you are uncovering. The steel reinforcement plate in the roof is supposed to be bonded to the fiberglass body. However, over time the glue looses it adhesion and the roof becomes too flexible. You can see this when you open the doors and the roof flexes. I fixed this problem by putting bolts through into the passenger compartment and installed a second plate inside the car. I also put liquid fiberglass inbetween the plate and body for bonding. This is much stronger than the original design. Bob Brandys 97 ? DeLorean