Had them fitted a week ago and it took the garage 2 hours. After the first few runs all seemed well and good with the car definitely feeling tighter in the turns - placebo effect I was telling myself! Still not as good as my B7 RS4 but hugely better than the boat the S4 was pretending to be like. But after a few days lots of knocking was coming from the front of the car. I took the car back to the garage today and they said there's hardly any room for the front bar to fit with the splash shield. In the end they shaved about 15mm off each side of the splash shield and all is good now

Slightly frustrating that H&R don't mention this in their instructions or indeed design appropriately.