I've tried a couple other Hot End Bowden conversions, but none fit the pneufit-type fitting I used. I decided to start from scratch in OpenSCAD and make my own.

First step was creation of a dimensionally accurate Ubis model (http://www.thingiverse.com/thing:103189). I used this with measurements from the Printrbot and pneufit adapter: SPC-06-01 Pneumatic Push to Connect Fitting. This fitting uses a British Standard Pipe Taper Thread R1/8". Tap size is 8.4mm for this thread, but I'm 'self' tapping with the thread itself into the plastic. I'm using 9.45mm for the base and 9.15 for the tip (it tapers.) I bought these from eBay (http://www.ebay.com/itm/Pneumatic-ONE-Push-In-Touch-to-Connect-Straight-male-Threaded-1-8-Tube-OD-6mm/290736473017?_trksid=p5197.m1992&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D14%26meid%3D8383794446985907354%26pid%3D100015%26prg%3D1006%26rk%3D1%26sd%3D290736473017%26)

I also used this fitting on my vertical extruder stand for the other side of the Bowden setup (http://www.thingiverse.com/thing:96940).

The pictured (and workign great!) item was printed at .8 infill. It used an earlier version of the model that had a thinner base and needed washers to make up the difference. The downloadable model has been reworked to be the proper height.