I was never able to get a fine enough grind for espresso with the machine before I shimmed the lower burrs up despite aligning the marks correctly. Although in testing I did once misalign them during an install and noticed considerably coarser grinds along the scale, so I assume my other installs were "correct"

That's true, out of the box the grinders sometimes don't grind fine enough. Did you get the shims directly from the manufacturer? Graef know about this problem and send shims for free to their customers if there is a problem with to coarse grinding. Not the most elegant solution to let customers modify their machines to get them grinding right but I guess you get what you pay for although for me the graef is still a good start in the espresso world.

I do not believe krups does such a thing, but I also didn't bother asking.

As a few other people in this thread did I simply used cardstock/thick paper and cut out my own shim.