Subjective?? Perhaps. If spending days working on an engine to get a couple hundred more rpm is worth your time when just changing a prop can do the same thing????? I'm set up to do some engine work with equipment that most people don't always have and I have still made a mistake and ended up with an engine that was running better before I worked on it. Oops can happen!! I'm pretty sure sure the no is a good answer for most people.