I mounted my XM in the front cap, over the Television. It gets shielded occasionally when facing due North, but I can live with it until I feel like moving it.
We use it with a Boom Box adapter unit with a built in antenna, so if we're going North for an extended period, we use the built in and set the radio by a side window.
2005 Georgetown 342DS XL, Full Banks Package
2005 Liberty Renegade 4X Toad
1989 Wrangler Sahara Toad
1984 19.5' Beachcraft i/o 5.o liter, 4-bbl (and you thought your Moho sucked gas!)
D/W Carole and Maggie the Teacup Lab (Black Chihuahua)