shimming for installed height

I need to shim another .030" to get my installed height where it needs to be. Now I have a .060" shim under the spring cup, if I try to put anymore shims under the cup the cup will not stay centered on the valve guide. My question is: can I put this .030" shim under the valve spring inside of the cup? The spring would still be captured by the cup and the cup would still be centered on the guide. The shims I am using are Comp Cams, they appear to be tool steel.
The springs are pac 1224, the diameter is 1.625, and open pressure is about 850 lbs. The seat pressure is about 265 lbs.
Author: Old School