Mr Goodworth
Attach a plate to the top of the block pictured with enough overhang to mount prop from lowerside and you are back to the easy position and referenced of the correct hub face.
And Man, can I get really picky now. When the USAF Folks were trying to make an acceptable facsimile of a B-36 mechanic out of me, we were taught that the face of the blade was the flat side and the back of the blade was the curvy part. And don't tell me that is backward cause the props are on the back side of that long wing.
Last Stunt Contest I ever flew was in 1959 and in those days I bought a prop and ran it cause I broke as many airplanes as I did props. I tend to be a realist and understood that, as in bowling and golfing, I was as good after learning the pattern that existed then, as I was ever gonna be.
The 50 odd years since, I have spent my time in the Speed Circle. Those years and 18 National Records later, I am still trying to sort things out. We do go to great lengths to get our dream of the correct prop. Know we will never get there but can show reasons for what we do. Any change in engine strength demands a change in the prop. Blade tracking and blade angle from blade to blade seem to be important. I can talk props a long time.
Double Deuce