Hmm, I am not convinced about the usefulness of an Adaptall to M42 adapter that a PK/M or a PK/A adapter would not have in this digital age.
I have read your posts regarding the fickleness of PK/A adapters, while there are some points that were new but mostly they are experiences of any of us dedicated Adaptall lenses users have encountered at one time or another - and found ways to work around them - while shooting with these wonderful legacy lenses. Considering the age of these adapters, I am thankful that they are still all working without problems. Anyway, to minimize the fickleness of the PK/A adapters to a minimum, I have outfitted every SP lenses (with aperture ring) with PK/A adapters and the rest with PK/M adapters. And so far, this strategy seem to be working fine.