Hi,
This is how I added shims
As the track is closed today (because snow), I change the oil and add 2 more shims. When I had only two, I put them between the plastic white shim. I don't know if it's the best position for them but it works for me.
When placing shims and o-rings, I recommend you use a little grease to allow the seal to be most effective producing less friction on the shock shaft. The movement will be smoother.
Best regards