Not to derail the thread and reargue the case for going ultralight, but I think 2lbs can make a meaningful difference. And if the comparison is between a SG Sky and a kifaru pack and frame of comparable size and similar organization, then the difference might actually be more than that when you add in hip belt, lid, and side pockets.
Unless you're very disciplined, it's easy to accumulate a surprising amount of weight. A pound or two here in the pack, another in the sleeping bag, eight ounces for the sleeping pad, a couple pounds extra for the tent, throw in an extra set of batteries and some extra ammo, how about another rifle just in case your main one fails, etc. And before you know it, your bag is full of stuff you'll never use, and it will weigh so much that it slows you down and holds you back--stuff you'll end up replacing because carrying it all is so tiring--and you won't have room for the extra things that matter. If your base weight is 12lbs the possibility of finding somewhere to cut two pounds from your pack is almost impossible--and two pounds is another day of food, another day of hunting, another day of opportunity (not to mention how much lighter it feels after three or four days of lugging a pack up and down mountainsides for fifteen hours a day). So, for me, if I can reduce the starting weight of my pack by two pounds, it's seriously worth considering.
All that said, I have three kifaru packs (none of them ultralight) and one stone glacier (so far) and I cannot imagine giving any of them up.
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