I drove the beetle, and my wife and my other daughter were in the “family” car chasing me. They overtook me a couple of times for taking pictures and videos.
The speed driven was approximately 100 km/h:
It’s hard to see what’s going on in the video’s, but we made some pictures too. These make it much more clear what is happening:
It’s striking that the tufts right below the spoiler are pointing upwards. Apparently there is turbulence, which is good. It means the airflow is detached from the car!
A close up diagonally behind:
Especially the outer two tufts on the spoiler show that the airflow is detached from the car.
After this run I stopped and removed the spoiler.