>While the X and Z axis don't require shims
I don't understand this.
I've been building a KRMx01. I used the new nuts. I found it necessary to make 1/8" shims for all of the axes.
Given that each axis is pretty similar in terms of rail to cross piece spacing, how would it *not* be the case that all axes needed to be shimmed?
Pics to follow if this is not clear.