Greg,
Thank you for sharing the rest of that info.

With regards to the 1.5" pipe out of the crank port, I put it on the passenger side pushing down into the block. This required a slight pinching of the pipe to slide in. I cut it at a 45 deg angle to help knock the oil off first.
I then put the pipe at a 90 deg angle and ran it down the back of the block and put the filler/canister with the scrubbers in it there.
As well I have tried a number of different materials for insertion to help drop the oil. Copper kitchen scrubbers worked the best.

Now this is on a strung 4.7L. You have much larger bores which of course is going to lead to a much higher volume of air having to move.
So that pipe may not be enough. However this car and my car have been run from roughly 80/100kmph up to 240kmph with zero oil injection present. Is this a 2 valve or a 4 valve 4.7?
This is a 2 Valve car. Though I will be doing the same thing shortly to my street car. On my street 32V 5.0L I have a 1" ID breather hose, and my dipstick has never popped out. It is NA

I would be very interested in how much oil was ejected from that hose during the run made. Lots of oil. Solid squirts from -10 hose. Probably 1/2 of a quart, from the head breathers. More from the crankcase.
I would be going from that -10 (5/8") up to a minimum of a -16 (1"). But as stated, I used a 1.5" ID pipe on that breather system. With the displacement of this motor, and that it is new with slightly more blowby (guesstimate) I would be considering 2x 1.5" pipes, or 2x 1" pipes coming out of that area. The slower the air speed, the faster the oil falls. I also cap off all my cam cover port, and have no leaking from them.

The other thing I would be interested in hearing is why you believe the 944S2 valve would not provide enough oil at idle. That head and cams are pretty much exaclt the same as the 928S4 head and I have not heard any issues with excessive cam wear. 944S2 engines are pretty low on bottom end torque and thus need to be "spun" much more. They put a lower ring and pinion into these cars, so that the engines could get up into the higher rpm ranges quicker. I'm not sure I've ever seen a 944S2 with an automatic. Note that the 968 vehicles did not use this restrictor. Scares me, on a street car.
With the document that shows the 944 valve posted just shortly before this, it indicates that it is a pressure limiting valve, also referred to as a pressure reducing valve. In operation is should allow full flow to the heads at lower RPMS, then it prevents the pressure to the heads from exceeding 3 bar. This should technically help to reduce the problem for sure. The other option would be to modify the heads for a different style of valve known as a priority valve. This valve would allow up to a specific GPM or LPM of oil to pass, and then shut off. It is commonly used to control the speed on a specific hyd rotation motor. This may be able to be worked out to use a stock hyd part. Or it may require a custom part to be machined.

Do you have any other ideas and thoughts as to why to oil is not exiting the heads? With both sides filling up, I think we can safely rule out the problem being caused by the whipping in the crank. The only thing left is an excessive flow of crankcase gasses. I think the fact that all of the head breathers "eject" oil at the same time, is significant. It would seen that the two sides of the block, with two different drain designs, would not fill at the exact same rate. To me, this points towards crankcase pressure and a giant "burp". My idea of the sequence of events is: The crankcase breather gets plugged with oil, the heads overwhelm the drains and start filling, the crankcase pressure rises, further blocking the oil from returning, the sump runs low on oil, and then there is a giant burp, when the crankcase pressure gets high enough.
I concur with your prognosis on the air burp. And while limiting the possible total flow to the heads might be a wise idea. I still believe that opening the breathing system from the main part of the crankcase up and capping off the cam cover ports might help to correct the problem.
The other thing which I will be doing and trying on my motor is to shim the stock pressure relief cartridge to a much higher pressure, and then run an externally adjustable pressure relief cartridge. I will at that time be reducing the maximum possible pressure to 80-85PSI. Because my engine is drysump, I can then tag this dumped oil right back into the pickup. On a street car this could be tagged into the drain plug to help it.