Remix of MakeALot's excellent Replicator 2 Fan Duct revisited.
Which I've now remixed this thing:

https://www.thingiverse.com/thing:3141321

Improved retainer clips and air flow. Plus, added features for easier 3D printing.

You will still need to tape a 2mm nugget on the extruder motor for the X axis home switch arm to hit. Shifts the build area, does not reduce it.

FYI, I wrapped the heat block with 2 layers of white ceramic insulation, then wrapped that with PTFE tape (pipe seal), and there's still pleanty of clearance. Also replaced the worn out nozzle and threaded tube with nickle XT coated parts. Now with this duct, my Rep2 rocks!

Parasoid X_T file of this rep 2 duct available in downloads.

Enjoy :)

EDIT 7/15/16: Added STAY_Rev2, for a more rigid hold. Recommend using washers with the mounting screws.