I like that example. I use a similar analogy to that frequently. If you are in a room with a ceiling that is even a few inches over your head you don't have to stoop at all. It doesn't necessarily benefit you if the ceiling is 3 inches over your head or 10 inches or 10 feet (with respect to walking that is - add some room for up and down etc.) On the other hand things become tremendously difficult if the ceiling is even an 1/8 of an inch lower than it needs to be. In that case you have to stoop and you can't walk normally.