I think it's reasonable with a little work to get the Kelty in the 4 to 5 pound range. I think when I removed the bottom shelf, top bracket and the wings, it was in the 3 plus range. Yes you need to work out a load shelf replacement, but that's doable.
I have never had luck with 3 piece belts and large loads. The crew cab was ok but the foam was harder than my hips liked, I did like the layout of the CC though.