Almost done with 12mm Z axis upgrade, extra long bearings, anti-backlash nuts, 2-1 gearing and to top it off a .9 stepper.
I will post pics, but it is amazing how much stiffer these are vs the 8mm and as such mitigate some frame torsion.
The upgrade required 10mm spacers for the bearings I printed before the upgrade, as well as drilling the LHF mounting holes and the bed, tedious and a bit scary, I replaced one at a time to maintain proper alignment.
Cost was about $100 minus the $25 for the stepper.
I also have a ATP-5 bed and AC mat on the way, as well as some 2020 to beef up the frame even more.
I'm turning this into a monster of an FT-5- what the FT-5 should have been, costs be damned.