I can report that I had a double-bass (far more fragile and sensitive than electric basses which are basically 2x4s) shipped from New England in fall to Texas. Temps from 35F to 85F during the trip. For all intents and purposes the bass was shipped in its padded bag, secured in the back of a truck so it didn't flop around and nothing fell on it. Of course there was no climate control inside the truck. I don't know what the humidity range was for that particular trip.
When I took it out of the bag it was still in tune.
You can stop worrying about shipping your basses in a container by ocean vessel. As I said, if your instrument came from anywhere to the US except Canada or Mexico, it was shipped in a container on a ship with no climate or humidity control. The very best scheme would be to have each one in a hard case to prevent accidental minor damage from impact should something shift in the container.
When I took it out of the bag it was still in tune.
You can stop worrying about shipping your basses in a container by ocean vessel. As I said, if your instrument came from anywhere to the US except Canada or Mexico, it was shipped in a container on a ship with no climate or humidity control. The very best scheme would be to have each one in a hard case to prevent accidental minor damage from impact should something shift in the container.