This is just a slightly modified version of funbarts great idea: http://www.thingiverse.com/thing:40524
It also requires to turn the fan blowing direction by turning the front fans.
Depending on your installed fans you might also have to print the shorter washers from funbarts thing.(Not required for me)
It's outlet is designed to directing the air a little more to the printed model instead on the upper part of the nozzle.
I made the fan collector cap a little wider and a little longer to allow removing the protection grill and almost fetch all air comming from the fans.
The duct itself is not as deep as the original to make sure there is a small gap of 5mm to the front of the printer in warming up possition.
Basically the clips give pretty good results when doing fine PLA prints without the need of an addtitional cooling fan.
For printing material like ABS they have to be removed!
V2 Update requested by user laird to match his needs and nozzle calibration: Bottom duct is 1.8mm less high. Back has a bridge wall and air outlet is modified a little to compensate the higher position of the duct bottom. Did my successful test print with ABS, 0.1mm layer hight, 1 shell and 100% of infill. Unfortunately black is not the best color to take a picture of. Of course PLA filament is fine for this print, too, but then you should use a temporary active fan to print these thin walls and bridges successfully.
I printed it with:
0.1mm layer hight
NO support (bridging worked well for me with temporal actiive cooling)
Make sure you didn't forget to reverse the fans by 180Â°!