I mounted mine at the top of the back window on the OUTSIDE of the car using silicone.
I have heard that the location of the antenna can change the quality of the signal.
For best reception the antenna should be able to see the sky as well as not go through glass. My friend with a camaro said that his signal quality increased alot when he mounted his antenna on a metal body part, too bad we don't have any of those.
Although you can see the antenna from the outside on my car, the look is very subtle. I will snap a pic and post it for ya later today.