I use a Wilderness safe packer for mountain biking. If you can wear your gun belt while riding your bike, it will ride nicely at 6 o'clock, out of the way, weight were it needs to be. However, if I am off road in rought terrain, like a single track, I find a belt very uncomfortable and almost impossible to wear. I attached the safe packer to my cross tube and my down tube with some extra Velcro straps. Weight in the center, protects the gun from mud and water. Its not waterproof so if you lay your bike down in a stream or mud bog, you will be cleaning.... Make sure you seal your permit and credentials in a ziplock. It will also fit in the safepacker. Its also nice to have the gun attached to your bike incase you take a fall. I couldn't imagine landing on my 1911 commander. That would hurt.....
http://thewilderness.com/catalog/pro...3a7fa254ee4cc6