An Ursack is definitely not need for the AT. All shelters and campsites that have bear problems have either a bear box or a food hanging system. Due to the rocky terrain you will be camping at an established shelter or campsite 95-100% of the time. Unestablished sites don’t have critter issues. All shelters have homemade but effective mice hangers. I’ve hiked the AT twice and animal problems are rare if you simply hang your food.
Yes, I’ve had mice and a critter get to my food. Usually they eat a small hole in your gorp or nimble on your chocolate and its no big deal. If you really want to carry an extra 20 oz. consider, a handful of snickers bars instead. The point is you won’t have a total loss and you can easily pop off the trail and get more food if needed.
You can make a lightweight windscreen out of a foil oven liner. Mine weighs only 1 oz. I punched some holes on the bottom. It folds and fits inside my pot with my pepsi can stove and stand.
Daybreak