Shims. Plastic, wood, metal, etc. Whatever is available and easiest for you to work with. Micro-Mark sells shims but why spend the extra money is you don't have to. Not sure the pattern is exactly the same with theirs either but it's close. I say this because I seem to remember there was a slight difference between the KD and the Atlas and the M-M shims are for KDs.
I could be wrong about the latter half of the preceding paragraph. I'm no expert on Atlas but I've done my fair share of shimming.
Jay