It's the movement that is the issue. I just received a trade and the naked sticks were destroyed from hitting each other freeze dried. Get the air out of the bag and either use 5 finger or cellos that fit. I suppose saran wrap or tissue gift wrap would do too. Usps has been notoriously late recently from weather. Plan 4 days for those 2 day boxes. Good luck!
People who send sticks loose in regular (non-5 finger) baggies, without wrap (bubble or saran) are just shipping carelessly, wouldn't matter if it were summer or winter for those sticks getting damaged.
mostly, but not necessarily. most of my shit is shipped out in standard baggies. BUT, most of my shit is double-bagged, and also wrapped with padding, which is sometimes bubble and sometimes just news.
what kills it is either impact or abrasion. impact is solved by padding, simple. abrasion, two fixes if you don't have finger bags handy: do NOT ship cello and non-cello together, and do NOT leave space to rattle around. if need be, ship everything without cello, or bag them separate. then reduce wiggle room by possibly something as simple as a ribbon or piece of tape on the outside of the bag, locking the contents down. another bag around that (extra layer of vapor barrier), then pad, seal, and label.
but we are really on the same page on this, a little thought and effort on the front side will go a long way...