The shim is located in a pocket created by drilling a hole in a 1.2mm Brass sheet. This sheet is then glued to a 3mm Brass sheet with, you've got it, Chemical Metal. The sandwich was then drilled to take the four fixing screws and cut to the correct shape. I made a gasket from 0.4mm gasket paper and located the shim in the pocket with a spot of silicone instant gasket. If you don’t do this it tends to stick to the spindle when lifted, due to oil viscosity and ends up out of its location. You would have to do a strip down to relocate it every time so it’s worth making sure it stays put.
I didn’t want to glue the shim in permanently, as I don’t know what the wear rates will be. Experience with the Thorens suggests it will be much slower than for the plastic pad, still the sealant will allow you to change shims if needed. Also remember, the circlip that normally retains the spindle can not be fitted due to lack of access, so you will have to press down on the spindle with your thumb when removing the platter, if you want to keep it in place.