I met this guy on the PCT(Pacific Crest Trail) last year. He has a site where he sells gear he makes. He also list his PCT gear list with a base weight of under 5lbs. (2.26kg)
See the pointing hat he’s wearing? It opens up flat so he could sit on it during his breaks.
Personally, I think, people who feel that their 4 oz packs are comfortable, just don’t know any better. But he does have great prices on cuben fiber stuff sacks and if you want a 4 oz pack this would be the place to get it.
Check out Samurai Joe’s site at http://www.zpacks.com