I also have the Cobra. I really like it. I have dual 4ft fiberglass antennas mounted on my rear bumper just like you were asking about. They really flopped around allot so I had to brace them to my tail light guards. (pictures below)
Inside the bumper is a thick metal plate that will need a very big hole drilled through it to run the antenna cable. It is allot of work but I think the outcome is well worth it.
Regards,
Jerry
Yellowh2.com
