The Post Office advised me to mail my small (up to 9 x 12 paintings on panels in their Document Envelopes (cardboard on either side). They said mail goes through a machine and can be damaged, but these work great. I put them in the sealed bags first. Do any of you do anything different? Also, for small Gallery Wrapped Canvas, say 6 x 6 or 8 x 8, I have been wrapping in bubble wrap and then putting either pieces of foam board or cardboard on back or front. Any other suggestions, and are there certain boxes that you can get for these? Just noticed another post on this, that recommended boxes from Amazon, but kind of hate to order 100 boxes! Thanks in advance for any tips!