The original design weights were not wrong as such, due to the layout of our car there was more weight at the back than expected. Terry said that this happens sometimes. I'm guessing its the heavy exhaust hanging out the back (and the birch ply floor) that's pushed the weight up.
The correct design weight for ours was:
500 axle 1
563 or above axle 2
1063 or above gross weight
Mark the tester said put 563 or more for the rear design weight which is what came out processing on the scales. I asked Terry to put:
500 1
565 2
1065 Gross
In the letter which was fine with Mark - 65 was a nicer number than 63 to go on the form
Basically the design weights needs to be higher than the actual weight of the car as it should take into account luggage / passengers / fuel.