Martin, the attached photos may not answer all your questions, but you may find them interesting. They are a selection of those I took while on our QE2 trip, and some show the manner of restraining the containers, while others show the huge numbers of containers in some of the ports we visited. I posted the shot of the damaged containers in Los Angeles some time ago, but I think it warrants repeating, if only to wonder again how the damage occurred. If you look closely at the first photo, you can see more damaged containers near the base of the crane.
Peter.