Back from the weigh bridge.
Trailer towed very well, no jumping, no rolling – just as it should be – very smooth.
The brakes are hyper good but that comes at a price .. I am 180kg over my originally
calculated weight. But that is what I expected, have more alu in the chassis than
originally planned, the air engine and the air tank was not in the calculation, cables,
brake lines, brake locks, bolts, lights .. it all adds up. The brakes and trailing arms are really  heavy duty and the luxury of having my dually wheels on the trailer cost another 45kg for the hub extensions. Each of the wheels with trailing arm etc is 150kg.
So now I will model all the actual changes and adjust the weight to get as close as possible to the measured weight.

Will weigh and double check the calculated weight for the baggage doors, awning, windows and everything else significant to get an idea where I end up, because we have to make the decision if we build the deck or not. If we build it I have to order the third door from the US, I want the same as the other  entry doors, it will take 3-4 months to get here by sea freight.

I still have the option of putting the second battery bank on the truck, which will give me
another 100kg payload. The truck is fine, I had all measurements taken from front axle, truck with trailer, the whole rig, the trailer axle weight and the trailer tare.

The ball weight is really good at 220kg, considering the very heavy steel brace and coupling mount at the front. It is 13% at the moment of the total trailer weight.
I expect to get up to 800kg depending really if I store the second battery bank in the front or not.
I mean the weight on the truck will be the same but it is different when weighed separately.
I plan to stay legal at all times with bot individual components, as it should be.
I don’t have to worry about the truck though. I have 1.3t payload and that already includes all the heavy extras on the truck, like tub cover, long range tank, steel bull bar and winch, roof rack, side steps and so on.
The main concern is how much payload we have left on the van after everything is done. The tools and spare parts I take will be in the truck.
It is going to be tight with all the gadgets fitted and I expect not more than 400kg net payload for personal stuff, food and water while driving. When parked and processing our water and filling the van tanks we will be higher of course, I am still hoping to get away with a final tare of 3.8 to 3.9t, which means 500-600kg payload.
Anyway, so far so good .. at least I am not 500kg over calculation – that would be a serious issue.