It is absolutely imperative that you secure the engine "up" as well as tying the plane down. If not, the engine mount may receive very high G shock loads. Many many planes are damaged n sea freight. Secure with HEAVY nylon straps through the engine bracket with the top cowl off. Remember not to leave anything lying around loose inside the plane. Some times the sea is gentle enough, but more often than not there are massive waves on ocean trips, and containers can get dropped a few feet in the unloading process. Make no assumptions, nor trust to luck, The plane and engine should be suspended both up and down. Also the wings are best secured by making flat steel plate inserts into the spar caps if you have removable wingtips. Make a wood or steel frame and secure it into the structure of the container. Tying everything down is only HALF the job. A 40 footer is adequate and some have done it in a 20, but the price difference is very little, usually. If you're in NH, Craig Sinclair at Hampton did this for me the last time, and my plane arrived without a scratch in England. We saved the packing material, and are now sending it to China. Le me know if you want photos. I'll have to look. Good luck!