I found the thread that I was talking about that PlayboyPenguin started a short time ago that eventually got closed. I know it's probably the run-of-the-mill pack. But, again, I'm kinda ignorant on the types out there. His seemed to be a bit more geared towards catering to concealing a gun as well as having easy access to your belongings in the same pack.
The only thing I see is it may not ride well for you positioned on the side as pictured. But, maybe you can still have it mounted, yes, over your fanny. The way the gun is positioned in the pack appears to be easily accessible even if you go that route and won't interfere with cycling.