Oh another thought, I am not sure if Simpson Motorsport 'pulled' the arches a little, I did mention that loosening fender mounts and a little adjusting then re tightening had also been mentioned.
The inner lip is rolled back and the inner arch moved upwards when they did this, not just bolt removed. I take your point, there is a real 'dipper' on one of my regular trips, when I had my E92 M3 I would hit the front spoiler on some occasions. This was a slow down point for me as it can throw the car around, even this was okay at speed and getting thrown around
I guess the answer might be very different if you get corner loading and a real awkward dip/bump. I'd like to try and see, but for a road car it has not been an issue so far (1,000 miles or so)