[spacemanspif]

I have to agree with Frank, the civic has a recessed windshield with a protruding a-pillar and I believe the new Focus and Fiesta have a similar set design. There was a post on here about Mercedes experimenting with a-pillar fences but can't remember it off the top of my head. Also, doesn't the old Beatle benefit from such fences? I'll have to do more digging when I'm not on my phone...

I think the original idea is a neat one just to try and block so much air coming into contact with the side mirror. Let the air up the pillar spill over like normal, but redirect some flow away from the problematic mirrors... Some triangles of coroplast should be easy enough to cut up and stick on for testing. Tuft test the windows and sides of the car and only treat 1 side so you can compare if there is extended turbulence on the non-treated side. I'm assuming the faster you regain attached flow, the better off you are.