ok, so a Sony VAIO VGN-T350P already delivers 5-7hrs actual batt life in a 3 pounds package.
http://www.tomshardware.co.uk/2005/0...e_sony_laptop/
Sure its expensive and even a refurbished version goes for $1600+ ... but hey, its doable.
http://www.tigerdirect.com/applicati...P=OTC-CNETFEED