almost all cdi flywheels have similar tapers...most can be adjusted with minimal effort, thus making the possibilities limitless. We managed to put a puch CDI on a twin bat motor using an internal pickup for the one cylinder, using a scooter CDI was placed an external pickup on a sliding engine mount holder that we bolted to the pickup close to the outside of the flywheel. We then welded on a small strip of metal to pass the pickup. Got both cylinders firing, one a few tenth of a mm off which ended up being limited by the motor mount pickup holder which we need to make an official bracket for. I was suprized how easily we made it work with just a puch cdi box and a pickup from some jank scooter shit left in a parts bin.
The advantage to a small rotor, well its pretty obvious...more rpm's. However the principal stays the same. I even like the idea that I could design my own cdi box that would advance the signal based on the circuitry that I learned in linear systems class. But then I'd have to have a much steadier hand and be able to solder.