Extruder barrel cooling duct for MK5-6 v6

This is a derivative of my own prior extruder barrel cooling duct. ( http://www.thingiverse.com/thing:8461 )

It is optimized for a 40mm fan, which won't fit inside the 35mm gap between the two large sides of a standard MK5-6 extruder. I find that PLA prints much better with active cooling directly on the barrel itself.

The section STL is for a replacement side to the extruder. It is functionally identical to the original small acrylic piece that fits there - except that it has a big rec