I've got the same camera and am trying to do exactly what you're talking about. I've run into the same problems. The only good setup that I have for it is on my AR. I used velcro to mount the base on the foregrip just forward of my support hand. gives just a little bit of the flash hider and pretty good view of down range. No problems with it coming loose yet.
Just can't get a good setup for the pistol yet. If I get a solution, I'll be sure to post it for you.