I've got a Sirius radio, the antenna head is slightly larger than 1"x1". I know from previous cars that it's not necessary to have the metal plane underneath the antenna to get good reception. I've always had good luck putting the antenna somewhere out of the way but near a window, which is why I'm aiming for the spot between the windshield and the rearview mirror. Anyway, I'll provide an update once it's done. Thanks for the feedback...