I am working on a modified OX with a belt drive rack and pinion system. It is really a modified F-117 and uses 80/20 5010 beams for the X and Y. Preliminary design gives a 6" Z with 50"x50" travel for the other axes. I am using cncrouterparts pro racks and made up belt drives. The cncrouterparts drives are just a bit to big to easily use in this design. See attached pics, comments welcome.