UPDATE: I've updated this to have a "to spec" version of the model that does not exactly match my E3Ds but is as is defined in the spec sheets. I have used this to create a new extruder for the MakerGear M2 and a duct for the E3D. The designs based on the "to spec" model worked just as well as my "real world" model. This allowed me to generate a highly precise model for a fan duct for the E3D v6 (http://www.thingiverse.com/thing:494430). I hope you all find it useful in your own design solutions for what is proving to be a robust and excellent hot end.
EDIT: I just completed a fan duct for v6 of the E3D hot end. To do this I made as accurate a rendition of the hot end that I could, which include the embedded Bowden coupling and the heater cartridge and a few other details so that I can precisely position fan elements. I based this design in part on the E3D technical drawings and my own hot ends. There are a few minor divergences from the E3D published design in my hot end. I don't know if they are universal or specific to the batch of hot ends in which mine were milled. I hope you find this useful in your own designs and please let me know if there is a design flaw. I haven't printed this as I didn't intend this to be printed.