I've been involved in eight out of nine blind exchanges. Two of the eight have been damaged. One by DHL and the other by the Post Office. In another exchange on the Large Format forum I was getting back 8 of my own prints in my own packing. Two sheets of 8 ply and two sheets of 4 ply. The idiot postman had to bend these over his knee to fit them in my postal box. He was the part time weekend man. Do not bend stamps all over. He did not care a bit.
Monday morning I was at the boss's office with the package in hand and foaming at the mouth mad. I never saw that post man again. With luck he's now delivering welfare checks in Newark, NJ.
I no longer send out mounted 8x10's. I send 5x7 Pt. prints mounted with plywood sheets as backer board. Let them bend that. The tubes are another good way to go but I like to send a mounted print.
BTW, the Post Office just a reported 3.8 billion loss this year.