Just found it.

https://www.rctech.net/forum/electri...ll-center.html

A simple way to remember that final part on ways to raise or lower the RC, is whether you are adjusting with spacers inside or out, or experimenting with different holes, they are all simply different ways to change the length of the rod. At the end of the day that is what matters in the adjustment. Rod length... Its 99% the same difference which method you prefer.. (Yes, their is a miniscule amount of nuance as to which method you choose, which you can look into if you see fit, but its very subtle and overcomplicates things..)

Using shim/spacer adjustments usually allows changes in smaller increments than changing holes, therefore less dramatic.