Edit: I have recently finished redesigning this thing, and have uploaded it to thingiverse here: http://www.thingiverse.com/thing:271506 This extruder is a mashup of several designs, mixed with a few of my own ideas. It allows you to use the stock carriages for the solidoodle while having an E3D hotend with an active cooling fan. It is made to allow for easy removal of the hotend, and also has a built in wire guide for cable management. I have drafted up some modifications to allow for better heatsink fan placement, but for now this design should work quite well. I will post pictures of the entire assembly when I can, because I just printed the fan last night. Thanks for looking! Due to the offset needed by the large size of the E3D heatsink fins, you will need to move your extruder stepper motor forward by around 4mm. This means that you will also have to unscrew the setscrew in the filament drive gear to move it further down the stepper motor shaft so that it aligns with the new offset hole. This may make the entire extruder assembly "front heavy", but it seems that it is working fine so far. I'm hoping to eventually redesign it from scratch to eliminate some workarounds that had to be done to get the mashup to work correctly. Please feel free to comment on any ideas you might have on improving this.