I have also had mine for coding and adjustment at Solms. Mine was backfocusing at the apertures you mentioned with about 10 cm at 2 meters. This was unworkable. After adjustment it front focuses with about 1,5 cm at full aparture. When stopped down, DOF moves backwards - and widens, of cause. Well, my eyesight is not all that perfect anymore so I will not engage in a heated dispute about the exact measurements. But now it works, somehow, with a little training and ideal conditions.
Which points at the problem working with the Noctilux; it demands a good eyesight - that of an eagle or Condor will be fine, to place the DOF correctly. I will recommend a viewfinder magnifier -
Leica Camera AG - Photography - LEICA VIEWFINDER MAGNIFIER M 1.25x & NEW 1.4x