I had a 5" wide magnetic mount (from a truck stop) with a 3' Wilson antenna for a while in the middle of my roof. Low tree branches knocked it off a few dozen too many times for my liking. Scratched the middle of the roof, too. It also blows off at about 80-90 mph. I even experimented with a spring in it for a little while - all the clunking around up there bugged me.

After I got the custom rear bumper, I also got a K40 5?-foot whip antenna and screwed it on back there. Reception is great, but I now understand why TLCA doesn't allow long whip antennas. It would bonk my spotters in the head if they were near the 4Runner on rocky sections, which was actually quite dangerous. So now I put a foam ball on the antenna and bungee it to my highlift jack half-way up the antenna so it doesn't whip all over the place. It's just what works for me. I still don't know what I'd do if I didn't have the custom bumpers.

I do have a friend (BlueDodge) that surprisingly has had VERY good luck with one of those small (18"?) antennas stuck on the window. It miraculously sends the signal through the window without drilling any holes and tested great with an SWR meter. As was mentioned above, his isn't mounted on a window with metal tinting on it.