Thanks for all the replies guys.
Blatt, do you hike with the scabbard under your pack? I can't imagine it being comfortable with a gun jammed in there between pack and back, not to mention the straps of the pack over the straps of the scabbard. I'm talking about hiking with a full 80 liter internal frame pack.
That aside, I can see how that would work really well with a pistol grip defender, but with my Grizzly, I don't have the option of the pistol grip. With the short barrel and the butt stock, I'd be trying to fish it out by the end of the butt, which I can see being problematic in a panic situation. I did a little playing around with some mocked up configurations and just didn't like the way the gun had to sit with the butt sticking way up out of the pack in order to be able to withdraw it quickly.
I'm hiking on Vancouver Island (home), and in the Chilcotin this summer. We've got cats around here, though I've yet to see one in person. And lots of Black Bears. I've had a few close encounters and been lucky in every one so far (wasn't packing). I'd expect the chances of needing to use it are pretty low, but I have no intentions of pushing my luck.
Single point is looking good. I'll have to try to mock something up and try it.