you can't measure the forces involved when cornering because there are too many variables.
Tyres are designed to stay in shape and remove heat efficiently if used within specification.
Stepping outside of the spec invites forces on the tyre it was simply not designed to cope with.
A fully loaded van can carry 2.4 tonnes the tyres recommended are there to keep this weight under control.
Suffice to say the load ratings are there for this reason...
Caravelles were designed to carry people, so there tyre load ratings are lower, because the van is not carrying the same weight as a panel van converted to a camper.
By the way if VOSA stop your van and weigh it, and if they find you are overweight on the back axle (over 1300kg ) you can expect a heavy fine and points.
AGG 2.0L 8V. (Golf GTi MkIII)