i have used them in both the "u" and "n" config. i find it easier to slide the "n" over the webbing, especially when i need to hang'em high.
i don't know for sure but, i think the upper edge of the webbing may have a little more tension on it so i use the "n" these days.
i'm just goofy that way?
oh yeah... that's the way the "master" does it !