Glad to help.
But... at the risk of sounding like a broken record, I think the folding stock/pistol grip thing is more likely to be a hindrance than a help if you do need to get at and use the shotgun quickly. If it's in a quick-draw setup, I could see a folded stock hanging up much more easily than a conventional one, and even if it doesn't, if you do need the gun right then, you'll have a choice between asking the bear to wait while you unfold the stock, or using the shotgun as a pistol-grip-only one.
The former is probably impractical, and the latter will seriously affect your ability to hit anything (much less make a CNS shot) with any type of load, much less one that produces as much recoil as the Brenneke slugs.
A short-barreled (18.5-inch) shotgun with a standard stock should fit fine in a case or scabbard, and won't project much, if at all -- depending on the dimensions of your pack, of course.
And if you turn up at the trap range with a folding stock and pistol grip on your gun, it won't make it any easier to learn. And traditionalists may laugh at you behind your back...