Nor would I try 40 pounds in a Vapor Trail - but the VT fits the lower end of Mumblez' requirement. The Nimbus Ozone is rated to 40 pounds, and weighs 3 pounds. I've used the Vapor Trail, and found the 30 pound rating pretty accurate; I have friends who have used the Nimbus Ozone and feel it's rated correctly, too.

I now use the Aether 60 (4 pounds, 45 pound rating) but am taking a serious look at the Exos 58: 2 pounds, 10 ounces, with a 35 pound rating. It fits Mumblez' requirement, except that it does have a lid and more bells and whistles (literally - there's a whistle built into the fastex clip on the sternum strap!) The jury is still out on it.