So I attempted to make my own version of a single fan with two points of cooling. I included some pics of mine and comparison to someone else’s that I found on here. The both work but I was trying to achieve a more equal airflow from each nozzle. In the end it works like a champ but it looks a little phalic to me… If anyone’s interested I’ll post the downloads later…
Interesting… I like the boxy look better… 
If using a round tunnel is more efficient, consider enclosing with a rectangular exterior.
Truth be told, the normal duct opening is to small to allow the compressed airflow of the 40mm fan through. You can test this by turning the fan full blast to 100%, you’ll feel the air coming through the back of the fan.
With that said, diverting the airflow with the vane (splitter) is smart… but may not be necessary.
Regardless, that’s a great job. I’m looking to design something similar for the dual extruder v2, so that the extrusion from each hotend can be cooled independently.
I have one that I decided was overkill that hits from four sides. But in reality I think just two open fans, one either side would do the trick with less headache. This was more I just wanted to print something than anything else.