Enlarging PRP doesn't always help

PRH said

In my limited testing of changing only the valve job from a 45 to a 50, the results were less lower/mid-lift flow, and no gains, or even a slight loss at the higher lifts.

Keep in mind these were tests done at the customers request, on a head that had to be usable after the testing was done.
So, pretty limited.
But I saw no magic from the 50.
I’m not saying it doesn’t work, but I can see where it would take actual R&D to be able to exploit it.

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The one data point that I have that I have confirmed several times is this. On the SM head with 50 degree seats, changing the top angle from 39 degrees to 45 degrees ON THE SHORT SIDE ONLY is worth 5-7 cfm because of the anti-reversion. I have only done this test with clay in the chamber due to the obvious difficulty of cutting a 39 deg top cut on 2/3 of the perimeter and a 45 degree top cut on the other 1/3.

Otherwise, with just a 50/39 vs a 45/35 I have seen a small low lift loss, but moderate gains in mid and high lift flow.