Simple mod to reduce/eliminate z-wobble. No extra hardware required.
Instructions (consult pictures):
Remove threaded rod and unscrew Z nut from X axis
Use screws from nut to attach part 1 to the top of the nut, screws from below
Put the nut back on threaded rod and install rod back to place
X axis should be resting on bumps at the top of part 1
Now use provided M4 screw to attach part 2 to the filament sensor screw hole from the top
Any z-wobble should now be eliminated
Friendly recommendation, don't use flexible couplings. I tried them and they only caused more problems.