So I guess I'm going to jump in on this and ask why I haven't had problems with Frankenstein?? Did I do enough wrongs to make a right? First, I have no problems with the oiling system. oil returns, and mostly stays inside the motor, except for some typical weeping at the valve covers and a little at the oil pump/case gasket, neither of which indicate anything but a backyard engineering job with inadequate sealing at these points.
With the Sporty pump and full flow to the pinion I'm adding more oil to the flywheel chamber over stock 45 I'm sure. With no breather slinger on the generator gear cause the gear just isn't there I've created another potential problem, and I also do not run the vent line from the cam chest to the oil tank. That hole is plugged off because the BSA Oil tank vents to atmosphere with no provision for the 45 vent line.
The end result is as I've said, the oil stays inside. The breather seems to be every bit as dry of oil mist as my "80SV. And as I've said, there's no sign of an unstable oil scavenging system. Maybe the lack of tank-cam chest connection is responsible for my differing results? I don't know, but it does work. I've certainly run the machine at high rpms and ridden it hard.
Don't pretend to have the answers, just relating my personal experience.