A very nicely put comment Prof, and one which I agree with. Err on the side of caution, drive with caution and load safely but there are so many variables further research would be very useful!
Further research. now there's another chestnut.
There is an often referred to piece of useful work carried out by the University of Bath on behalf of Bailey Caravans in nearby Bristol. The paper defined a number of characteristics that affect the towing behaviour of a caravan behind a car. The work produced a model that was demonstrated at several locations that showed how the load distribution on a trailer can affect the handling of a car and trailer combination. The demonstration was quite dramatic, and I applaud the intention and hopefully it made some of its audience think a little more about how to distribute load in their caravan.
The demo was very dramatic, and it did help to explain the principal of the point that was being made, but what it did not do was to fairly represent a real car and caravan. There were some significant deviations from the real car and caravan actually used in the project.
The project did come to some cogent conclusions, but the evidence and results only came from one car and one caravan, so the specific results and conclusions cannot be assumed to be equally applicable to all outfits. (that's why i'm not quoting the results)
That demonstrates the point of this comment. To generate enough practical evidence to be able to produce a universal stability formula would be a never ending project, which would continue to grow in complexity as every new car or caravan was produced.
I actually discussed the idea of this with a couple of ex Uni' of Bath Masters of automotive engineering, and there is passion to do something, but no funding to even start the ground work to explore the scope of the project.
As Lutz has pointed out above and on a number of previous threads, the UK is as far as I know unique in having this type of industry advice, Perhaps it would make more sense to study how other countries do manage to keep stability failure so low.
One suggestion concludes its the practice on continental caravans to have longer A frames. But also its more common for caravans to be fitted with suspension dampers.....and the list goes on.