Oh, for sure it’s way more work than I’d take on.
But it looks like that’s a “test head”, so it’s not so bad only doing one port to test the theories.
With “normal” porting...... no holes, no sleeves, no extraordinairy measure......... an X head can get into the 270’s, and not have the numbers get too terrible at the top end of the flow curve.
I’m more conservative at the short turn on the 915 and later heads....... as I prefer not finding water there.