Nicks linear actuator paste extruder

I started with the modified paste extruder available on thingiverse, but quickly found I needed a more accurate extruder.
I moved to a modified syringe pump based extruder but needed one that worked how I wanted (and could do dual extrusion!
I took a (relatively) cheap linear actuator I found on ebay (http://www.ebay.com/itm/STEPPER-MOTOR-LEADSCREW-LA23GCKB-1-LINEAR-ACTUATOR-/290996217983?pt=LH_DefaultDomain_0&hash=item43c0b9e87f) and designed a small "box" to constrain it.
Briefly, I plac