Where I work, we have this plastic film( stretch wrap) that we use to wrap around pallets of stuff to keep it clean and together so it doesn't fall apart. Just think of it as super heavy duty Saran wrap.

Anyway, I roll up big balls of it and stuff it into a feed sack. I stuff it clear full. I paint a few dots on it and hang it up.

It will stop an arrow and yet allow two finger removal.

I have also heard of guys stuffing feed sacks with rags and old clothing. Make sure snaps, zippers, buttonsand rivets are removed.