Since seeing the E46 M3 CSL, I've always been a huge fan of CSL's subtlety when it come to styling, especially with the trademark duck tail. I found that it looked powerful but at the same time refined.
While the car was in the shop for its respray, I asked for the Brabus rear boot lid spoiler that was already fitted (shown below) to be smoothed into the boot lid to re-create the CSL look.
The standard Brabus spoiler was used to get the main shape, with the outer edges extended to the very corners of the boot lid to give it that factory look.
As you can see, it makes quite a difference to the rear end. It's in fitting with the rest of the car and doesn't look like an aftermarket 'stick on' spoiler.