I have to admit that was more effort than I'd have taken for an OS .
Your point about the pipe is correct regardless of the engine.

Tommy,
As to speed you will find that the 9x8 will give you much more potential than the 10x7 even at the same rpm, but you will get even more RPM. The Diameter address the drag and acceleration issue. Pitch deals with speed. And yes rpm is important to the overall performance of the prop. The ability of a prop to absorb power is related the Diameter to the 4th power and RPM to the 3rd power, Pitch is a linear. Since pitch speed is RPM times pitch it is a benefit to loose some Diameter to gain RPM if speed is the goal.