Another vote for the Safepacker. I hike a lot on the AT in NC, GA, TN and VA. We have a fair share of hippies and granola crunchers that would just mess themselves at seeing a firearm on the trail. The Safepacker helps avoid those annoying encounters since it just looks like another piece of gear.
It's hard to see in the pics, but the safepacker has a "flap" that wraps around the entire back side of the holster. It is large enough to wrap around the pack belt on my Gregory pack. So, it ends up mounting like any other belt holster.
Also, it's easy to detach at the end of the day for hand carry, over the shoulder (with a strap) or attach to your pants belt.