Shims are a normal part of a bolt on guitar setup. Shims for the neck, shims for the locking nut, and sometimes even shims for other things.
The shims that EBMM uses are plastic, and measure 0.254mm, 0.381mm, and 0.508mm. The 0.6mm shim you suggest would be larger than the largest EBMM shims.
Can you see the shims that the tech put in? It really sounds like you should read up on how to properly set up a guitar before attempting anything further. I don't think razor blades would be the best thing to use for a shim.
What is the current action on the guitar? Factory string setting for standard tuning starts at the bass side 2/32" (1.59 mm) to 5/64" (1.98 mm) and the treble side is 3/64" (1.19 mm) to 2/32" (1.59 mm) measured from the 12th fret to the bottom of the strings. If you are looking for an action lower than that, the guitars really aren't designed to go much lower.
The razor blades was just a glimpse. I can get a piece of wood as thin as a razor blade for the nut.
I'll try to measure the tension but the question is just esthetic, the neck is totally straight, the tension are very comfortable, but the pieces of plastic used to shim really bother me.
I don't need some super low string tension, the setup in my Axis are great, I think I can make the same work, but more "cleaner" the actual one. And wood sounds and looks better than plastic pieces if I need to explain that to somebody.
Shimming are news to me (since 2019), and I don't imagine how important that is to setup the Axis, for people like me, who don't know nothing about this until some time ago, sounds bad.
I don't care a lot about shim anymore and I got the point of it.
But, just to think about:
If you have two Axis, same year, same color, same everything, but one have shims and another didn't, which one do you choose?
