The Hadron is a great 3D-Printer, I was one of the first user and I don't want to miss it. This is one of my improvements for the Hadron, it's derived from brnrd's thing:38534.
Update 23 Jan, 2013
Going on with the Z-Wobble improvement the diameter can be reduced to 10mm.
Update 27 Jan, 2013
Increased tolerance to off-center. (14x11.2mm)
Slicer Settings I used:
Layer height: 0.25 mm
Fill density: 0.4
Speed: 50 mm/s
Nozzle diameter: 0.35 mm
The mounting holes in the Z-AxisBlock are meant to be tapped with M5 threads (I used a M5 screw).
Mount the parts according to the image. You need 4 additional M5x9mm screws.
Update Z-AxisBlockV2 and Z-AxisBlockV3:
We don't need to tap the holes with M5 threads, instead we can use M4 screws and nuts to mount the Z-AxisBlock and have the screws well tighten.