Here's some different test pressures and the valve turned upside down. I really thought the dip would go away at the lower test pressures. It did not. It's also interesting that the port flows more with the valve than without. Some people say they have never had it occur. I've seen it several times. Maybe it's just my screwed up methodology. Actually it's just the valve creating a floor to the flow zone and improving the pressure recovery in the chamber.
I also tried a 10-15 degree soft quench pad on the long side to try to deshroud the 0.600-0.700 lift area. Almost no change. I really thought it would help. Back to head scratching.
One last point. At 28 in, max flow before loss of the short turn (0.550 lift) is equal to the flow with the valve turned upside down. This means something. Not sure what, but it's a clue to something.