I've figured out a way to use the fan based on kafarn work : http://www.thingiverse.com/thing:794860 Since I'm still using the geeetech PLA mount plate for the MK8 extruder, my design here provides a way to do so, without even bothering to attach anything (the PLA fan duct just fit around the fan, no screws). I'm thinking about making the duct end turned 90° on the left : it would get easier to print (not that is that hard actually), but maybe a little tricky to get the distance with the nozzle right.