3D Printer 4xLM8UU Minimal X Carriage (with symmetric/balanced tensioning mechanism) for F694zz bearings & more [#SCOUTcorexy design]

This is the evolution of the 3xLM8UU Minimal X-Carriage with balanced belt-tensioner (http://www.thingiverse.com/thing:1505842) that I have previously developed for __SCOUTcorexy 3D Printed (http://www.thingiverse.com/thing:1487375)__.

It is not replacing it as that one servers the purpose very well but this is an effort to have 4 bearings for those who want them.

I made this one modular so I or anybody else can just replace the belt-grippers at will, printing them alone if the bearings o