Not so keen on 2 motors off one driver.

Also for step alignment I will loosen one coupling, turn them on, then tighten the coupling. I think this will get the motors aligned internally.

Here is the machine as a reminder:
Click image for larger version.  Name: Z_dualaxis2.png  Views: 629  Size: 1,014.0 KB  ID: 30378

Click image for larger version.  Name: Z_dualaxis.png  Views: 657  Size: 732.5 KB  ID: 30379