I think the Backpack vs. Bag needs some tweaking. A full backpack will save 20% of 30 lbs (6 lbs total), but costs 2 lbs for a net 4 lb gain. 2 bags require the same materials, but save you 20% of 40 lbs (8 lbs total) costing 0.6 lbs for a net gain of 7.2 lbs. I think only the furnace is more than 20 lbs – everything else can fit in a bag – so there’s no good reason to make a backpack currently.