That's where my (real) XM antenna is.

You can kinda see it right behind the glass sitting on the rear deck of my car in this pic:
http://www.threxx.com/car/DSC00518.JPG

 

yeah thats how ive got mine mounted, on the passenger side up front in the corner of the windshield, and the GPS receiver for the eclipse AVN2454 setup same position opposite side. both work perfectly. i think the new xm antennas are a lot smaller than they used to be as well, from the looks of darius' pic, my xm is about 1/4 of the size and it still works fine....there are a lot of dealers who will not install the xm inside the car though. they claim it will not work and destroys reception. its also an easy way out of not having to do trial and error with the customer to see if it will work, to keep them from having to come back and waste more time on the car. eh.