After 34 views and no response I figured either no one has ever shimmed their needles or it was a really dumb question. Either way I decided to try the shims in both positions and then measure the height of the needles. Problem solved, the shims go between the plastic spacer and the bottom of the slide.
I must have really had a senior (Doh!) moment the last time I had the carbs apart because I had shims on both sides of the spacer. No consistency across the cylinders. Man it sucks getting old.
To compensate I decided to treat the bandit to some tuning and general maintenance. After some back and forth between tweaks, driving, and reading plugs I got it close. I then replaced the oil with some fresh Mobile 1, added one more shim, and then went through the sadistic process of syncing the carbs.
I just got back from a test ride and I think things are dialed in. The midrange is absolutely spot on.