Shipping the finished product

I got kind of a shock when I shipped my first dulcimer actually built for a customer. I dropped it off at a service that packed and shipped it. It wound up costing over $22 to ship a 20-1/2" dulcimer from Maryland to Louisiana.

I need to do better in the future and that probably means I need to cut out the middle man. I am looking for tips on packing and shipping my dulcimers.

Looking at shipping calculators it seems that box dimensions are the bigger issue than weight of the package. How much bigger does the box need to be? Where do you find suitable boxes? What packing material do you use.

Any suggestions on how to find the best rates?