I believe Austin's FCC 2.5 moved up and down about 3mm, it had the most armature play of any TW motor I've seen so far lol
Mine wasn't much better before I reshimmed it
Although I think they mounted their armature too low on the shaft, every time I reshim an armature the shaft is .2mm shy of the end of the bearing. Whereas the systema usually sticks out of the bearing a little. So with the FCC you have to mount the pinion gear fairly high and loctite it in place, whereas the systema you can bottom it out on the flat, ensuring it will never ride down.