The L is kind of big on me when it doesn't have stuff in it. The strap is shortened all the way down already, and there's a tad bit of room already. I would worry that the bag would be just too darn uncomfortable and big when it's not chock full o' stuff.

FWIW, I've never been like, "damn, I wish I could fit more crap into my bag" and I ride mine every day, all day.