Anyone install XM/Sirius in a targa?

[finaltable]

I have a cassette adapter XM unit for my car. Since I am replacing the head unit anyway I thought I'd put in one that has XM built in. I'd like to have the antenna mounted on the outside of the vehicle but I am not certain where to put it. The targa roof gives me pretty limited space on top unless I can somehow get the cable from the head unit up into the B pillar. The hood doesn't seem a good choice and the hatch seems problematic. Anyone else "solve" this problem?