Thanks to Buzz for this tip - an ultralight rolling bag. The Landor & Hawa Sub-0-G bag is 42.5 linear inches and weighs 4.8 pounds. The low weight is apparenlty achiieved by using aircraft-grade fiberglass instead of aluminum for the frame.
Gadling no has a detailed look at this wispy bag with large and helpful photos. Thanks to Scott at Gadling for acknowledging OBOW!