Fact is, however, that caravans aren't weighed as they come off the production line and manufacturers aren't under any obligation to do so. I would suspect that manufacturers would even oppose the idea of weighing each caravan on the grounds that they cannot guarantee that the weight doesn't change before the caravan is handed over to the customer, because the dealer may, in the interim, add items such as a motor mover, a spare wheel, etc.
If the caravan manufacturer restricts the MTPLM to a value significantly less than the chassis load allowance, one could argue that the chassis is overengineered because it is capable of carrying a higher load than required. A chain is only as strong as its weakest link.
That could well be true, I have not access to the dealer's contract with his manufacturer to check how robustly they specify.
However, we included a contractual clause with our dealer that the available payload to us on delivery should not be less than an agreed value. [300kgs]
On delivery as agreed it was weighed on load cells and found to be I think I recall 62 kgs over the maximum weight it could be, for the plated MTPLM.
That instigated a lot of behind the scenes activity, with the outcome of them offering the MTPLM being replated up to the chassis limit, and a request we please settle for a shortfall of the order of 20 kgs; which we did.
Buying in a professional manner, with such vital things contracted, is IMO the only way that will move towards getting the payloads we require. As it is presently offered, it is a meaningless dreamworld figure, IMO one typically pathetic for starters and even that one rarely achieved.