Mike,
Interesting concept, that of larger bubbles dissipating faster, thus causing the pump to deliver more actual oil. I'm not sure I understand why the filter would make the bubbles larger. It seems the intuitive opposite, but, I suspect you have considered this more than I and have a good explanation.
Regarding the scavenge side sucking up the same amount as the feed side delivers, ultimately, this is trying to happen, but the circumstances by which this happens are different for the two functions. The feed side has the benefit of constant atmospheric pressure in the tank and gravity sending oil toward the pump. The scavenge side must depend on siphon created by the pump, as allowed by air pressure in the crankcase, which, in turn, is dependent on pressure allowed in and out by the breather. As we know, the breather is infrequently open. Is it not possible that the inefficiecy of siphoning versus gravity (as helped by atmospheric pressure) makes the back pressure of the lines and filter more critical, particularly if the action of siphoning, itself, is normally contributing to reducing crankcase air pressure? Though I have no confirmation from previous discussion in this forum, I am convinced that the main purpose of the breather is to create near-normal atmospheric pressure in the crankcase so that oil can be pumped in and drawn out.
Another aspect that has received little comment here is valve guides. Bill suggested this as a possibiliity, believing they had not been mentioned. Going back, we see that you had the head rebuilt, including guides. For my understanding, guides would have been a more obvious and direct source of oil loss than excess oil on the backside of the oil scraper ring. Having new guides does not guarantee that they fit properly. However, I suppose that if it were guides, smoke would be more continuous.
I trust that I have only ventured into things I understand while attempting to make it sound like I understand that of which I speak. Nevertheless, I always appreciate being set straight when I've strayed from the path.
Richard
P.S. As an electronics engineer (I believe in the UK), perhaps you can help me on another issue completely. My work requires me to understand a bit about 3-phase electrical power in the UK/EU. So, my question is: should I refer to UK 3-phase as 240/415 VAC, 230/400 VAC or somethng else completely. Anyone else knowing the answer, please feel free to jump in. Sorry, if this strays too far from our prime directive of exploring the exotic world of A7/10's.
P.P.S. I modified my P.S., after-the-fact, to more closely resemble how we in the U.S. might rever to 3-phase, as in "120/208" (phase-to-neutral/phase-to-phase). Now I really have tortured the reader's patience for miles-off-topic.