Don't count on racking a shotgun...
It's not only that maybe it wouldn't work as a deterrent, or maybe the "drunk neighbor's daughter" maybe won't hear it, in the couple of HD situations I've found myself in, the last thing I wanted to do was make any sound at all.
Regarding the sling: when your heart is already making more noise than you'd like, a sling will sound to you like a log chain dragging through a pile of empty beer cans. Bad idea for discreet indoor needs.
Les