If I'm following the notes correctly, as well as the photos, it looks exactly like LM8LUU (long version) linear bearings in those photos.
I was starting to wonder if the rods were hardened steel, otherwise, such bearings would eventually groove and lead to backlash/play.
But after reading @Matfink's post several times, if I understand correctly, the linear bearings are what he took OUT of the FLUX, and replaced it with some sort of sleeve bushing??? I have no clue what spec is on that part.
If I'm tracking all this, then I am really confused as to what to do, or can be done to improve anything on the FLUX at this point.
I do know for a fact that the tool head does tilt on occasion, I've got it on video (which I did not notice until after I uploaded to YT) but it's there, the tool head is definitely at an angle.