Quick note - (now, climbers don't jump on me - this is not about double ropes and single ropes) - the smallest line diameter - regardless of fiber - used for that sort of thing is 8mm "personal rescue line" or "self rescue line". And not any old 8mm kernmantle will do. And they are NOT fall-rated.

I have some of it - enough to egress my office from my windows - and it's tiny enough to scare the bejabbers out of me. If I ever use it - window or wilds - I guarantee I'll have that coppery taste in my mouth, complete with rocketing blood pressure and pounding pulse... I like my 10.5 and 11mm ropes just fine, thank you, and I'll stick to 12mm for rescues if I have a choice.

I can and have broken 550 cord - easily - I would not trust my life to it, period. I'll find another way...

Whew! Makes me break out in a sweat thinking about it, LoL! I love 550 cord - been using it for almost 30 years - but not for lowering anything heavier than my rucksack. Although I carry 550 cord... as I've stated before, I prefer Dacron cord of slightly larger diameter than 550 for general utility cord. Not as "SAK" a cordage as 550 cord, but it has many virtues that endear it to me.

I think I carry about the same stuff you do - a bit more cordage, but same things (love that bright mason's twine) plus the Dacron as my "workhorse" for non-climbing apps. Plus waxed linen (floss), carpet thread, and a hank of very heavy nylon thread used for repairing cargo parachute webbing. (No, not all in my PSK!)