I don't have the equipment to do precision drilling for the lm8uu holders, and adding a belt tensioning system to the wooden carriage eats up Z printable space. So my solution is to design my own Y carriage with build in belt tensioning.Please check out V2 of this here http://www.thingiverse.com/thing:12979The stl files with the makergear suffix are for Makergear Prusa Mendel and should be a drop-in replacement for their wooden y-carriage. This is the set that i have printed, tested and am currently using.The stl files without suffix are sized for standard Prusa Mendel. However due to me not having a standard Prusa Mendel, they have not been printed or otherwise tested in anyway by me.. so you will be at your own risk if you decide to give them a try.Also enclosed are the scad files, you can change the dimension to whatever you need in there.