You have too much prop when the engine cannot make the rated rpm static, or perform to the specifications in flight for cruise/top end.
You have too little prop when you cannot make the lowest advertised cruise speed or top speed with the engine running at or very near the redline. You can also feel the prop being spun too fast because it will cavatate or stall while trying to make thrust. You cannot select your prop based on how your engine works with partial power or you never will have an efficient prop. Your emergency procedures and practice of those procedures are how you deal with that, not design the plane to crash well. Colin N96TA
