TTF, what’s your strategy? Do you want to go ultra-light (sub 20lb.), light (20-30), or higher (30-40lbs.)? There’s only a few places on the AT where you will need a larger pack for storage (ie. 100 Mile Wilderness in Maine). There are some hostels in Monson that may cache some food for you – so even there you might be able to get away with a smaller pack. If you carry a tent -there’s some 2 lbs options you should look at.