This will basically be an Ultimaker-like design (bowden extruder head). The main differences will be using Microrax instead of both the laser-cut side pieces and the linear bearings. Either bearings will run on directly on the extrusion or we'll use the nylon shower rollers listed in the Linear Motion section.
Bowden extruder info:
Use this hot-end:
PFTE 1/8ID (1/4" OD) tube source: