I already have done the window with string test and i do have it on video. The air seperates about 3/4 of the way down the rear window. My question is how do you test the air on and around the wing?
I suppose you could also do the string test there, but I know F1 has used the oil trick in the past. With the oil test, you simply put droplets of oil on the rear spoiler where you want to test the direction of flow. Short of having a wind tunnel, I'm not sure what other options you have.