Shims come in all kinds of sizes and thicknesses - if you ever need any go to McMaster-Carr and search on shim - they have them just about any way you can imagine. They are specified by OD x ID X thk - have both inch and metric. I forget what size I use for UE 6 and 8 sypder work, but I'll start there.

Where you have placed the shims basically moves the ring gear toward the pinion, so I guess thats where the slop is - the ring sits too low and mesh is poor. Cool - would be easy if you didn't have to open the diff. I'll try it on my ST where I'm still using gear diffs.

Thanks!