A large been bag that we made several years ago has become expensive to
feed.

We regularly get another bag of polystyrene beads, bung them in, say
'That's better'. No sooner do we get used to it being full than the
filling compresses again.

Aside from anything else, the bag is getting rather heavy now! (OK - at
least two of its regular users are heavier than average.)

Any suggestions for how to reduce its appetite? Is there anything else
we can stuff it with?