Mendel Inspired Drop-In Makerbot Y-Stage

I was doing some Mendel research and discovered this great video about how it\'s axes work: http://vimeo.com/6982104

It inspired me to try to build my own, and naturally, I started with Makerbot\'s y-stage.

There are two versions of this design: (one for old-school makerbots and one for the new guys)
The makerbot who\'s axes I\'m redesigning is super old school and has the original 8mm steel rods (instead of the current ~6.3mm). Luckily parametric modeling means changing the design to ac