109 prop pitch (rpm) and the supercharger

[Crumpp]

Regarding the gain of airspeed at altitude by overevving the engine and "boosting" the supercharger this way, the F-1/F-2 Kennblatt gives some hint. Blatt 6 says that by increasing RPM to 2800 over the normal maximum of 2600 yields 10 to 15 kph increase in speed at the rated altitude.

Exactly....

As the speed increases, they will have to coarsen pitch to maintain rpm.