I love this swap. Its great digging through my stash looking for goodies for my partner.
As for the PO when I was mailing the address swap back if I had managed to get the envelope an even thinkness it would have still been considered an envelope and not a package. LOL but since I wasn't able to they charged me a package price. My PO workers were very apologetic and even had to work together to figure it out but they had a little slot on a card that explained what you had to do depending on what slot the envelope fit through.