You say that bo, but Audi recently sent me a photo of what looks like a normal 3 door with a roof rack on - see the attached photo.
This is apparently a Thule bar and I've really not got a clue how it attaches on. Here's the gents reply when I asked;
These are made by Thule but have been through extensive testing with Audi for them to be approved so you should not need to worry about the rear one falling off, if you get your credit card and gently put it in the top seal where the rear bar fits (as in the picture) you will see under the seal there is a guide for the roof bar to fit, if you have any concerns please contact me. If you are interested in purchasing these items I have no problem ordering them in so you can see how they fit,
Looking at the picture I can only presume he means at the top of the window seal?