Mount with 3 LM8UU linear bearings and 4 x M4 bolts rather than the original 2.
Bad photo, but you get the Idea.
Printrbot to a 3 bearing design, It should now perform better and be more stable doing this.
Above is the new design, below is the original - Note you don't loose any X axis movement or printing area with the Quick-Fit mount.
Files for the Printrbot Quick-Fit X carriage are up on Thingiverse Here.
While I was in the middle of drawing this for the Printrbot, a quick-fit adapter for Huxley was requested, as they share a vertical X arrangement, it should be possible. I'm just a little worried it will use up all of Huxley's X space!
#30DoC Day 5 - for inspirational work from around the world
I'm not obsessed with Extruder's and X carriages, I just really like them :)
** - Also Awesome things are happening over at the Unfold-Fab, right now, do take a look.
Thanks for looking, let me know if you have a Printrbot (built up) and also if you print one of these.