I would suggest removing the screw and after cleaning the threads apply some blue Locktite to the threads and replace, tightening to where it is clocked. The blue Locktite is not permanent so the screw can be removed. I have little faith in the shim method. Under the head it might raise the screw enough to interfere with the closing of the top lever.
Think about this bad advice...
The screw will look good being timed, but it won't be properly tightened. Loose stock screws permit the action to move under recoil. And eventually the wood cracks or splits.
The thin wood shim is a good solution for starters. And glass bedding may be advisable if things are really loose, or cracking of the wood has already started. But if having the screw slot timed perfectly under the top lever is important, it may take some trial and error for the proper shim thickness to get you there.