Benny, one more thing you can do is get a get a bunch of the #4 Priority boxes
Product: Priority Mail Box O-BOX4 (if you want your box to be 7" x 7" or a bunch of the #7 boxes
Product: Priority Mail Box O-BOX4 to create a box 12" x 12". If you took 12 of the #4 boxes or 9 of the #7 boxes and stacked them on top of one another, you'd get a box 72" long. I would tape the flaps together inside the box as well as on the outside. It would take quite a bit of tape but the Post Office might have their tape at a table or counter. They used to let you order the Priority Mail tape online for free, but they no longer offer it (my local Postmaster will give me a roll if I ask for it, but I prefer to use the stronger 3M tape anyways).
I've done this before for some other smaller things, but not bananas. However, I was reminded about it when I got a plant shipped to me in 4 of the #4 boxes yesterday.
This can create a very rigid box since the entire box is double-walled.
You can order all of these supplies online and they'll deliver them in a week or so to your home.
Category - Priority Mail
If you do this, let us know how it works and post a photo (or video)!
Harvey