QUBD TwoUp Z axis 2nd motor mod

Got tired of the sagging X axis and the pulley mod is limited in help.

Remixed Stephanburger parts and modified them so they mirror correctly and the idle pulle screw faces the back now.

Big difference in quality! 0.05 mm layers using a 0.25 mm hot end. Made 20 layers thin lithopanes with this mod without any problems.

Note that you need to move the existing Y axis motor to the center of the base together with the belt. That will also get rid of the "sideways jerk" that this printer has