I've been doing this wrong all along then? I've got my filter on the outtake side. What is the difference I wonder.
I've also heard airflow dynamics arguments, but I feel like I've heard them argued in both directions.
With a #9, one-inch filter, a single fan does fine.
Intake still allows the air coming out to be more turbulent, mixing with the existing air better and giving it more "throw" in larger spaces.
https://www.youtube.com/watch?v=zE4qmN_EOXw
edit1: exact time of the result https://youtu.be/zE4qmN_EOXw?t=250