well not only was the scavenge side deeply scored, but also the end plate for the oil pump was not fully tightened (one turn opened) ...once tightened, the pump would not move at all. In an attempt to keep the screws in this semi-loose position the PO has dot punched to "lock" the screws" (Why the hell people do such things is beyond me).
I agree, that if the non return valve does indeed play a role in this, then SRM have given crappy advice to not even mention this. As mechanics, SRM are obviously no better (or perhaps worse) than you're average classic mechanic, but they do make the parts which are otherwise not available, so i am happy they're there!!