I know you can 'track your ship' these days but how do you know your container is still on it?
Via GPS (at least for US bound shipments) - I mean the container themselves can have their own GPS transmitter. In cross border shipping of containers in N. America, truckers too have their container GPS tracked and logged (ie. where they've stopped and for how long)
Placement of container on the vessel isn't so much of a concern as humidity problems. You say you want it at the bottom of the load (where condensation is at most persistent?) You say you want the container at the top where it has the most varying temperature?
Our motorhome we bought from the UK 2 years go was shipped ex-Southampton port (RORO rate).