Measure the rims (we can all see this by the way.) Mavic had/have a habit of using a different measurement to the standard and you added 3mm (or possible more) on. So measure that. You hub measurement in the calculator are wrong.
With rima at 528 you'll have 256/258mm spokes, that's not right, the rims only 19mm deep and I would expect. ERD to be in the 540/541 region.
Great, thanks for the advice. Im waiting for the rims to be delivered, so will measure them when they arrive.