Interesting question and discussion. I have a home built CDI ignition that is controlled by a MicroChip PIC 16F627. I cannot tell you how CH works, but I can explain my design. To set the Hall sensor/magnet combination I also recommend slowly rotating the prop until the spark fires and adjusting this to occur at 32 deg BTDC.

What is happening in the software is the PIC chip is looking for the Hall sensor signal and when it triggers it measures that it is at X RPM. It then calculates the spark delay time Y for X RPM and starts counting down the prescribed Y microseconds (really scaled computer cycles to be exact). Since all this is happening very fast and you are rotating the prop very slowly the observed spark is almost instantaneous despite the fact that the PIC might be thinking the RPM is much higher and the delay should be 12 deg BTDC.

To see more of my PIC/CDI module go to http://home.earthlink.net/~marlowedc/CDI.htm