The clipping on that one wave will probably go away if you set volts per division higher. Or there might be something to set on the display. The high output means you might be able to adjust timing by moving the pickup in and out, since shrinking the wave effectively changes where in the rotation it crosses the voltage threshold to be detected, depends on how pronounced the ramping up is. Magnetic pickup probably means you can use a steel washer attached to the rotor instead of a magnet. If you want to limit a too high output, a voltage divider look up voltage divider formula, will lower the amplitude without affecting the shape.
That seems as a Splendid idea
A steel washer attached on the rotor can save $ 150 --- $ 200 dollar in fabrication and realization costs and can be moved.
And if need be a much smaller hole -- drilled for fastening. ..perhaps done without removing the rotor
perhaps a quick small spot weld is possible MIG or TIG Some wet rags around for cooling that might be doable or other Maybe soldering with a gas flame . ..