Chains
I don't have much to add to the advice above except to say that we shipped a lot of aircraft across the Atlantic during the 80's & 90's and found that most of the damage was as a result of ropes and nylon ratchet straps coming loose during the sea journey.
Eventually we used hooks chains and turnbuckles to secure the aircraft, if the situation required something soft to secure the aircraft we used the shortest rope we could and tensioned it with chains & a turnbuckle.
After a few lessons we had a zero damage shipments but I dread to think what the security people were thinking when they x-rayed my chain filled suit case on the way out to the USA !