I mailed my blind exhange print to France on Friday. I sandwiched the mounted and matted print (mounted on foam core, overall size 12X12") between 2 oversized pieces of heavy 3 ply mount board (each about 3/16" thick), taped the sandwich tight, and stuffed it in an oversized padded enveloped. With any luck, it'll arrive intact! Airmail postage wasn't unreasobable at all and the expected transit time is 4 to 7 days.