What kind of setup are you going with?
i have an '03 M3 so i can do sirius w/o any modulator/adaptor - that seems to be the way to go since i am pre-wired. i had planned to remove the center baby teather on the parcel shelf and fabricate an aluminum plate to stick the antenna on(painted black of course) - i also figured with a clear view it would receive signal - thanks for the feedback! a metal plate attatched through the baby teather bolt-hole would be as well grounded as putting it on the roof, the metal would be under the antenna - basically replicating a roof mount. I can't see any downside to doing it this way.