If you're shipping pieces like this yourself, foam packing is the way to go. Some packers can do it, or you can buy a setup for about $100. You basically put the item in a plastic bag, then spray this foam stuff in the bottom of the box. You lay another piece of plasic over the wet foam and lay the piece inside. Then you put another piece of plastic, and more foam. The stuff dries hard, completely supporting the item.
I don't have a setup myself, but I'ver bought a few pieces from an ebay power seller who ships all their glass this way, and I've been really impressed.
Laura