Hello Graham,
You state:
"At least you took the effort to test rather than go with the various theoretical possibilities. It would be a nice little exercise for PC to run a lab test aver a range of caravans to validate the findings and to finally dispel the fud factor and old wives stories about noseweights."
Let me first assure that the possibilities are more than theories, they are based just as much on real testing as Surfers and your own results. The theories support the findings which show that twin axle nose weight is a complex issue and there is no simple relationship between hight difference and weight difference for TA's.
The results that both you and Surfer have demonstrate there are differences in the readings depending on the method used. However I cannot make the same assumption that the error is only a few Kg. It depends on exactly how you made the measurements. The differences may be much bigger compared to the measurement at the ride height of the coupling which is where the limit is applicable.
There would be no practical results produced if anyone tested the nose weights of a selection of caravans, as the noseweight changes when loads are added or moved inside a caravan,and they also depend on the measurement height.
I'm sorry but your ill advised if to make simple assumptions about TA nose weight measurements.