And a problem like this wouldn't be complete without a facepalm. I just noticed with the stepper attached to my RedCat, if I ran it from 0 (fully retracted) to nearly max (500) and then back to 0, it kept missing the zero point by a few degrees (it was always short). It turns out the grub/set screw for the pulley attached to the stepper is loose. Double-d'oh! That means I have at least 10+ steps of backlash. I'm guessing it will work much better with a tight pulley.