We get quite a few props in for repair via UPS or FEDEX or USPS and I always hate opening a box filled with the dreaded styrofoam popcorn packing. It flies all over the place when you try to remove the prop, and a slight gust of wind sends the stuff everywhere. I usually end up on my hands and knees chasing the little rascals across the floor.
Here's what I do to contain the little buggers: Fold the box flaps up, and secure them to each other at each corner, making the box taller. Pull the prop out. The flaps contain the popcorn. Deposit box with popcorn intact in dumpster.
So keep those props coming, no matter how you pack them. I'll deal with it. But don't count on getting your popcorn back.