Hans,
Sorry, I was in a rush, didn't check the links. I see it is a 2 m pattern plane.
As it is 2 m long also the tail arm is likely to be long so a big tail arm likely. Do the calculations because the answer could well put the CG at 41%. There is no point ballasting up, or even worse positioning the equipment, to achieve a CG at 30% if it it wrong!!!
Manufacturers are sometimes wrong, but give them a chance - check their figures with the formula.
Alasdair