I've bought several backglasses from Mayfair and he ships them like this:

Wrapped tightly in brown craft paper, cardboard corner protectors, layers of bubble wrap, then packed in an outer box with peanuts.

Probably overkill but they always arrive perfectly!

My inlaws use to have a glass shop, so last year before they shut the business down i had them ship about 20 backglass for me. Did not have a single complaint from any of the buyers.

The glass was wrapped in paper, then was placed on a 1 1/2 insh think piece of styrofoam. The styrofoam was cut about 3 inches past each edge. Then another piece of styrofoam was placed on top and cut the same size of the other. Then packing tape was used tightly to hold the pieces together. Was kinda taped like a tictactoe game. Then the whole sandwich was wrapped in a layer of cardboard. Everything always arrived safely.

Since they were a glass company, they had supplies on hand to do this, The styrofoam and the card board would be bought by the pallet load in 5 foot by 10 foot pieces. so it was always custome cut to each piece. I dont know of any local places that sell that size, but im guessing that you could maybe buy smaller sizes like 4 feet x 4 feet and a place like lowes or home depot

I was actualy really worried about shipping the glass, one was a Kiss backglass that sold for 350.00 but he assured me it would be safe. He then asked if I had a glass that i didnt care about. I had some old backglass that had so much flaking it was almost plain glass. He packed it up, the pushed it of his store counter. We opened it up and it was fine

Just borrow locally someone's CPR backglass box.

Give it back when you are done with it.

Good design, never had a broken glass with them yet, and I've reused their boxes many times both ways.

Good info on packing a backglass on the BGResto site.

http://bgresto.com/?page_id=777