I actually just ordered an anvil spoiler for mine but before I did I had been doing a lot of research on what to do about the antenna and found a thread where the guy put the antenna attached to the rear bumper, from what I read it worked fine. I saved the link because that's exactly what I am going to do when I install the new spoiler.
This is the link if you're interested, I think its the best rout to go.
http://www.camaro5.com/forums/showthread.php?t=272540