when camping with the boy scouts, your sleeping bag needs to be in a water proof sack. which for us means stuff them in a garbage bag and then stuff them in their stuff sack. phooey. so i was helping. i started stuffing the sleeping bag into the garbage bag. then started stuffing the partially stuffed garbage and sleeping bag combo into the stuff sack. this worked pretty well. remarkably well. creepily well. when i was done, the sleeping bag was stuffed into the stuff sack far more compactly than normal. hrm. thought about that one for a while. usually it's a lot of work just to get the sleeping bag stuffed into the stuff sack at all. the garbage bag changed the game. my working theory is without the garbage bag the sleeping bag tends to expand as soon as you let up on it to grab the next handful of sleeping bag to stuff into the stuff sack. it expands by drawing air through the stuff sack. which it can't do when it's inside a garbage bag inside a stuff sack. cool. so if you ever need to stuff a sleeping bag extra small, now you know how. science is my bitch.