Kristi said, "Whoops, guess I should have mentioned treatment presupposes a cased dulcimer. "
I was thinking "cased", too. I would wrap the instrument in cloth and then fill in packing materials in all the empty spaces. Close the case. Then I would wrap the case in bubblewrap because I've never had a problem with it, if it's not right next to the wood inside the case. Now comes the more difficult decisions. How valuable is this instrument? Is it irreplaceable? How far is it traveling? Who's shipping it? If you followed the advice to put it in a "corregated cardboard cement form tube" then you'd just shove it in there, fill in the spaces, fill in both end, tape, and you're pretty much done. But I've never done it that way, so my experiences is only with cardboard boxes.
You will pay a whole lot of money to ship UPS, esp. if they pack it. I've personally had experiences where shipping the dulcimer was more than the price I paid for it--that just doesn't make sense!!!! If I have the time to pack it well and send it USPS, then that's what I do. It saves a lot of money, but you do need to pack it well! If you can double box it, that's best. But if you can't, then PLEASE get a VERY STURDY corregated board shipping box, add extra pieces of cardboard front, back, wrap cardboard around the ends of the case, and make sure ALL the spaces are filled. Shake it. Add more.
Just please do NOT use a box that a vacuum cleaner came in from the department store, etc. They have no STRUCTURAL INTEGRITY--"the ability of an item to hold together under a load, including its own weight, resisting breakage or bending.' You have to assume rough treatment by shippers. When you get done packing this instrument, you should at least be confident that IF you stood on it--but don't!!!--then the package would not bend, collapse, etc. If that's too hard to wrap your mind around, then think about it being at the bottom of a stack of boxes--and each of those boxes on top of it are holding a case of copy paper or two....
I once had an irreplaceable instrument sent to me in a practically indestructable instrument case--that I was not able to buy--and then paid to have the case shipped back across the country...and that was the right solution for that item. The case was then packed, as I described above, in a sturdy outer box.
I had someone send me an instrument that was rattling around in a box with a few sheets of newspaper crushed into balls at the bottom of the box. That it survived the trip of 100 miles without even being in a case is, in fact, a miracle.
Hope these tips help. Just don't put yourself in a position where if something goes wrong, you say "I should've".......