I've used the original mk8 direct drive hinged extruder for quite a while now with my E3D V5 with dual fan for reliable PLA cooling and it just works for me, amazing design.

However planning to update to E3D V6 I needed to modify the design a bit and for more reliable flexible printing etc I thought to allow the PTFE tubing run through the whole extruder frame so that you can insert a long tube, cut a hole to the spot where the motor gear and bearing are located, then allow the tube to continue all the way to the hotend.

So tl:dr; V6 compatible, mounting points for two fans, 4mm hole through the whole frame for PTFE tubing.

I uploaded two files from this, one with dual fan mounting holes as seen in pictures and one with the original left side fan mount only.

NOTE: I don't have the V6 hotend yet, so I can't test the actual fit for now.

UPDATE: 10th Nov. 2015

• Added "Extruder_dual_loose.stl" with 0.2mm bigger holes all around the hotend/PTFE mounting. This should solve the tolerance issues on some printers and make assembly easier. The original design is still valid if you want a "tight fit" extruder and have your printer calibrated properly.