You may never get a return package because of postage due. I get it on my end "the receiver".
Only if I refuse it does it go back to sender. Since I bought the chips and highly await them as a new addition to my Illegal collection I ALWAYS accept the postage dues as not top get the chips lost in the mail.

My post office will not let me send the bubble mailer for the flate rate. They told me I have to pay the "package or parcel" rate. We have argued this a couple times at the counter as I argue it is not over 3/4" thick (I read that anything 1/4" to 3/4" can go as a flat). They tell me that doesn't matter.

Now the real problem. The post office need to promulgate this on their web site "IN BOLD BLACK AND WHITE". It is a gray area for sure.