Didn't Sierra Designs steal your idea and build a whole line of bags with elastic panels to allow stretch for larger persons/sprawlers? Are some of the Montbell bags similar?

Actually, it's a great idea, Jim. The best part, versus buying a built-in stretch design, is that your bag snugs in where YOU need it to snug in, not where some designer guesses most people need it to be snug.

In warmer weather, using my WM Mitylite as a quilt accomplishes something similar: I kind of tuck it around me to minimize large air spaces. Sometimes it even works.