GN brought up a good additional point about materials. If someone has a basket full of forgings of a certain material "A" what good does mapping a prop do when I have a prop from another material "B". Even Bobs17-4 prop could have been heat treated about 6 different ways. I'll bet there has been more recent engineering on sails than on the drive line of our boats. How does one guys shaft bushing go away in months and another goes years. can't all be owner error. The tolerance build-up on some setups might be beyond belief.