I have bought and sold several using the triangle shaped priority mail boxes that the postal service provides to send rolled up documents. They seem to be pretty stiff and tough. I wrap the recurve in bubble wrap and piece two or three of the boxes together to make the length. I reinforce the boxes with mailing tape. This seems to work great. You have to send the bows priority mail because of the boxes. The boxes are free at your local post office.

Gar