Printrbot Simple extruder fan mount

My Printrbot Simple occasionally has a problem with the extruder overheating during long prints. Other people also report having this problem, and have mounted fans to keep the extruder cool. This is my design for a 40mm fan mount, which works quite well.

I followed the suggestion by Nathaniel Chapman to power the fan from the heated bed port (which is unused); this requires putting a 100K jumper on the T-BED connection to simulate a thermistor, and adding some gcode to the slicer (M140 S60 to turn on the fan, M140 S0 to turn it off).