mine is in a closet along the same wall as the closet door, flat against the wall leaning against the door frame (someone wouldn't see it just looking in the closet, friends/family mainly). But I am single with no children or anyone to worry about messing with it right now. It is cruiser ready with 4 00-buck reduced recoil loads. 3 more 00-buck and 2 full power slugs (turned the other direction so I know which is which) in a butt-cuff.
Not saying it's wrong, but I wouldn't keep my SD shotgun with the chamber opened. The risk is very low that something could find it's way in there or the shell might start to roll out (or at least enough to cause a jam) if you didn't pick up and hold it correctly while grabbing for it and racking forward, but there *is* a chance.