Ok I did some testing with a pretty good basic setup, on which I was trying to detect some kind of minimum height kind of setting for Front and Rear heights, while trying to keep the diffuser effect on following straight.
Unfortunately, the diffuser effect is pretty much lost above 25mm in front and 54mm in the back (with 20/48 wings). And I hit sth 2 times in Eau Rouge at that height.
The first one, I was looking for hitting sth along the inside curb and did hit it in a quite high position pretty much no responsible driver would go anyway.
But the second one can be easily touched even if you know it's there...
here's a link to a zip file containing captures. 3 shots for each spot found:
https://www.dropbox.com/s/u0ze412qmqztm0q/EauRougeGlitch.Testing.Spa2015.Captures.zip?dl=0
the orange arrows are pointing right to the area concerned, except for the one with 2 orange arrows, where the spot is between the tips of both the arrows, I'd say pretty close to the border between yellow and red curb's squares.
in the last of the first spot ones, the yellow arrow shows the front right wheel crashing, but in fact it's the bottom board hitting the ground an litterally "stopping" the car, the back of it passing right over the front. So I'd guess it's the effect of the pressure applied by the back of car moving suddenly up.