I've shipped a couple and if your buyer has the time just use the post office ground w/insurance. By far the cheapest. If time is a factor I use Priority. I used UPS for a long time. I just got tired of spending too much and they need a physical address unlike the post office who can use P.O. Boxes. I always put my motors in a plastic milk crate and then in a cardboard box just big enough to fit the crate. That way they can drop it or what ever and it doesn't brake. Don't know about wooden crates but I'll bet they don't care.
'02 Honda 416ex - A seasoned blend of 11 herbs and spices
'04 Honda Recon - The yard machine and snow plow
'88 Honda CR250R - Another chapter in my torrid all terrain affair