Are these shims you got tapered? If not (and even if they are) I feel there is a better way to do what I think you're needing to do.
Adjustable PUSHRODS. They will go shorter than stock. So if you're using stock rockers and the block and/or heads have been shaved necessitating the shims to adjust lifter preload and/or maintain rocker geometry, I prefer adjustable pushrods. You accomplish everything in one simple step.
However, if you aren't running stock rockers and had the block and/or heads cut.....then you're on your own.
Just make sure the shims are tapered for a proper fit.