Tell me about your setup. I am going to get an xm radio and here is my situation.
I need something easy to transfer b/c I'm in a different truck everyday. And there is nothing for a magnetic antennae to stick to.
you can put the antenna on the dash with little velcro or tape and it will work fine, most units come with a suction cup mount and a a/c vent mount and lighter plug for power
You can put the antenna on the dash. I did for a long time, but I found a 'metal plate' at the Flyin J. It's got a hole in it, for the CB antenna. It bolts in between the antenna, and the mirror bracket. (I'm sorry I don't have a picture) It works perfect. I crack the winder, just enough to get the coax through. You should find that 'metal plate' in the CB accessories section at the Flyin J or any other truck stop. I think it cost me around $7.oo.