I have the Inv (?) in mine, I have a short tether for the power chord and Ant hanging out of the bottom of the radio hole, and the unit it self sits in the area under my single DIN stereo in front of the CD pocket I have underneath it, also, if I want to close the door, I can shove the Sirius in the CD pocket and close it all up.
Also, I have the Magnet mount antenna inside the car on the rear deck, stuck to one of the speaker grates. No problem on reception
I'll try to get some pics later today.
edit; just checked the Sirius site for dimensions, and the Starmate is a little longer than the InV, but the same height, so if you have a pocket, it should work.