FWIW, if I had to ship parts I used multiple boxes taped together to cover the part. Overlapping the layers of carboard where they're spliced together and taped makes the box stronger than a single layer box.
Since long boxes used to ship parts are few and far between I started making my own from partial smaller boxes for economy, that ended hunting through store bins for the right size. I never had anyone get in touch with me that said the container didn't hold up
..........YMMV