Has any one had trouble focusing with Helical focus mounted digitars? I am using the 24, 35, and 60mm Digitars on my Alpa 12 SWA. I have followed the instructions for shimming the adapter for my H1 mount Aptus 22. I can find a shim combo that works for each lens, but each lens needs a different shim ammount than the others. Do the lenses need to be returned? Does Schneider or Alpa make shims that go into the lens mounts themselves?