Best non-roof rack bicycle carrier?

[DivideBYZero]

As title. I don't want a roof rack on an M3, it'll just look sheiser. Idealy I'm after something like the Saris Bones, but the site claims it doesn't fit, and after seeing one on the back of an A4 at my local trails I would agree, as it only just cleared the boot lip and that lid is much shorter than the E92.

Ideas?