SilverMk2, are these shims you are talking about under the brackets marked L and R. I have a sunroof that is out of another car, and the left and right bracket each has two shims under the plate. It looks to me that removing a shim would put more pressure on the rods that the springs ride on. I think the real problem may not be the mechanism at all. The sunroof gasket has a metal strip over the length of the rubber in the back of the gasket with five holes to hold it flat and screw it to the back of the sun roof. This rusts and bubbles up just like the metal in the trim, and it looks to me that it is more than enough to keep the roof from seating properly because the rust in some places on this unit I am looking at has raised almost a quarter of an inch. Most of this strip is gone, and I am betting that in the car, this rust has broken off and washed to the corners where it packs up and keeps the roof from seating, and may also contribute to clogging up the drains . I have a new gasket to compare it to, and I think the fix is to replace the gasket. It looks to me that you have to drop the headliner, and unbolt the pan that holds the sunroof and mechanism to the roof to replace the sunroof gasket. There is another gasket on the edge of this pan sealing it to the roof, and some will tear and stay in the car, so it looks like a RTV seal will have to be made on this torn gasket when it goes back together. I'll check to see if this gasket is still available, but I'm betting that this one is not.