RAMPS based Camera Slide from a 3D Printer Bits Version 2

A while ago I designed a 3D printer. It was big and slow and then I broke the thermister and got pissed off with the whole project. After a joyful afternoon dismantling the thing I had an awful lot of interesting 3D printed bits, some great techy stuff, and a RAMPS board to play with. I decided to build a camera slide for timelapse photography. This was described here:
http://www.thingiverse.com/thing:907355. It had a few issues.

So I pulled together a slightly different selection of bi