Most everyone here in Australia mounts their antenna on the front bar...usually on the centre loop. Most bars here come with 2+ antenna mounts on them.
Not the most close up pic, but you can see where it mounts.
Of course, we use 80 channel UHF for our CB's here....not sure what you guys are using in the way of frequency range (are you using 27mhz?).
UHF antennas seem to work best when you get them out away from the vehicle, so the bar is a popular place. The roof is a top spot for antenna performance, and probably the best place to get your antenna ripped off the first time you go off road, lol.