Finally got around to changing the BB oil (actually, finally got around to posting about my changing the BB oil a few weeks back); was about 2000 miles since the installation of the '2nd gen' BB - thus my first time changing the oil with the new BB; my findings:
Overall condition was OK...not great based on the color...but I have seen worse. No metallic shavings or anything floating around in there, so that is great. In total, 12oz of fluid drained out of BB - but since drain plug is not on exact bottom of case, there is room for a few more ounces to be hiding in there.
I also loosened the fill plug on tcase to see if any oil came out of there (which would indicate some is passing through seals b/w BB and tcase). There was a tiny gush of air when I loosened the plug, so it was little bit pressurized, and some fluid did leak out (2ozs total).
So, it does seem like there is some BB fluid passing through seal into tcase...but not much.
According to
@MountNGoat - upon close inspection of interior of the new BB case, there isn't a way to totally prevent oil migration through the seals (his words = "bearing around shaft where it exits to the tcase will not stop oil migration because it isn't press-fit; eventually the grease in the 'sealed' bearing will get displaced by oil").
I'm hoping it stays manageable, and the quantity of oil migration doesn't increase...because 2ozs over 2000 miles doesn't worry me...but I will be keeping an eye on this.
So, 12ozs drained out of BB + 2ozs migrated into tcase + whatever was left in BB below the the drain plug (~1 - 2ozs I'm assuming) is roughly consistent with what I understand to be the recommended (by NorthWest Fab) amount of oil it should hold.
I filled the BB with approx 16ozs of redline heavy shockproof gear oil - and am paying close attention to the catch-can at end of BB breather (so far, still no burpage - and thermax stickers have not registered a higher temp than before), and when I change the oil the next time, I will compare measured amounts that come out of the case(s) and post additional findings/insights here.
I still am not convinced if the external oil supply (being pumped out of BB drain, through cooler+filter+pump, and then back into the new 3rd-port...which I used as a fill port...on the other side of BB case) is necessary or not - though it probably is recommendable nonetheless (if for no other reason than to lengthen time/mileage between oil changes by increasing the total volume of oil that circulates in BB) but I sure am glad that the 3rd port now exists regardless; it was SO MUCH EASIER to change the oil (vs. having to inject through the breather port) and having the ability to add the external oil supply in the future gives peace of mind.