Simple dual bowden Extruder for Prusa i3 rework

Update:
--> Tested and working flawlessly, no issues with cooling and airflow.

an update under works: light rig setup under the fan

I had the following Design goals:
-single fan, enhanced airflow duct to maximise cooling and reduce fan noise.
-using common E3D extruder body and alu heatsink
-Keep minimum distance between heads (now at 24mm), still need to work on parametric approach (which started with 40mm).
-easy to disassemble (you know, jamming/cleaning and so on). Due to closeness of the heads, I could not have 2 clamps.
-clamp with pass-through screws (no need for inset nuts).
-structural rigidity
-fanduct, supported with a dent intrusion behind extruders.
-small part count (3) and printable (to be tested).
-easy disassembly/assembly (tested).

-BOM :
2/3 50mmxM3 screws.
3 M3 nuts

Used few models for this:
-derived from http://www.thingiverse.com/thing:547706 but as source was in Solidworks, created openscad version.
-Parametric fan blade http://www.thingiverse.com/thing:689564
-E3D extruder http://www.thingiverse.com/thing:433258

Disclaimer: I have printed couple iterations, this has been improved:
-M4 nut insets
-Fanduct support (simplified, with just dent on back seems good enough)
-Extruder separation
-Increased length and diameter for larger extruder
Now with pictures !