Adjustable Z top mount

A number of things can get the Geeetech i3 Pro B frame out of alignment, and for me it was the tension from the x axis belt which twisted the z axis screw and guide.
You can solve those problem in other ways, but I found that an adjustable z top mount was the simplest.
You probably only need this on one side, but I made two just because it looked good :)

Included is a version similar to the original part, and one version for a 608zz ball bearing, reducing friction from the spinning screw.