Mini Kossel groove mount
The groove mount that I received with my J-Head from MakerFarm was too large to fit underneath the effector and had through holes in the wrong locations. I quickly drew up this modified groove mount in OpenSCAD.
Update 7/14/2013:
I've uploaded an updated version which performs better and is inspired by goopyplastic's design. If you want the first version for some reason, see my Github repo below.