What do you mean
2" of shim rings? If it's under the stem, they're not shims - they're spacers used to adjust the stem height.
What's the diameter of your steerer tube and the stem's steerer clamp? Using a shim to reduce the diameter by one size is not uncommon. The shim is placed inside the stem's steerer clamp in between the fork's steerer tube.
To adjust your headset, the top cap is tightened down first to provide preload on the bearings until there is no more play. The stem clamp bolts are then tightened which holds the stem in place over the bearings. DO NOT GREASE THE CLAMPING SURFACE.
Parktool provides a very good tutorial:
Threadless Headset Service