Thanks for all the ideas.
Around here, quite a few have the same style of whip. Depending on the terrain, it can be left full up. or bent over and clipped to the roof so there's no issues with branches at all. Just depends where the trail is. I plan on putting a spring on it so it's a bit more forgiving. Rear bumper I know is the safest, but at the same time just to the side makes more sense. Do need to protect it somewhat if I do it that way, not that I'm running into things all the time, but do have to expect the unexpected.
I have some stainless steel brackets I was going to use on my leaf springs but never did, so I was thinking of possibly making a custom bracket with one of those , keeping it close to the body so it doesn't stick out very much. As for SWR, I asked about that, and the guy at the CB place said it's something I really needn't be overly concerned about with my application, but said I would need a proper length of cable to connect the CB and the antenna though. If I were wanting to test the SWR though, how would I go about doing that?
From the XJ's I've seen though seems the two places they always are attached though are the passenger quarter panel, or off of the bumper.