Lucian,
Adding a shim has more to do with which pressure plate you are using and the geometry of the fingers. If you were still using a new style ACT2600 the clutch fork would not be that far off to the driver side as the fingers on the pressure plate would be more parallel to the flywheel. This is why new style ACT pp's need a little more throw.

Looks like the CFDF clutch you are using is very close to stock. You don't need a shim here. If you do want to put one in anyways, keep it no more than 1mm.

Looking at the way your pp fingers are sitting, I predict you pedal will be light and engagement point will be high