I did another PTU drain and fill today (and took the pic's above). I measured the amount of fluid I drained and it was 400 ML and I suppose some residual in the drain pan etc. - so short of the 530 ml the manual says. The last time I filled it, it was at the bottom of the fill hole and this time when I removed the fill plug there was a bit of oil dripping out of it so I'm not losing any oil. The front was up on some 6" ramps so perhaps that is the difference as well since the fill hole is at the back of the PTU. Next time I'll try putting the back up on the ramps as see what I put in (if I can get at the PTU properly). There could be some more sludge still in the PTU also as the oil is still coming out black but not nearly as pudding like as it did originally.
Regarding a question I had about sort of a sucking sound when I first remove the fill plug and whether or not my vent was working, as suggested, I tried blowing air into the bottom drain hole and I could hear air coming out from somewhere. I put my fingers up at the vent and it didn't seem to be coming out from that - so it's a mystery. However I do know that it does vent - from somewhere - so it's not building up any pressure when it gets hot which is good.
I also tried probing the drain hole to see if I could insert a temperature probe. Unfortunately there is something just inside to the front of the PTU hole which would probably prevent me from inserting anything. Maybe I'll just glue a temperature sensor to the outside and watch that to see how high it goes. Hopefully my heat shield extension and regular oil changes will keep the temperature a bit cooler and not cook the oil. It doesn't seem to smell or appear burnt at all. If I was to drill another hole, I'd move it back about 1/2" and then probably would have a clear hole to insert a probe.