From the factory the driver FETs are running around 90C, which makes the hardware designer in me itch. So after seeing a couple other versions, including methods that require modding the controller board, I settled on this method.
Note that the fan is suspended between the grill and surface of the machine. In my experience this maximizes the efficiency of the fan.
Uploaded to https://www.thingiverse.com/thing:7325963 for your enjoyment.
Upcoming mod will be using a full 5V to drive the fan. As is, the highest I've seen the driver temperature is 57C.