R/C Plane CDI - Hall Sensor Questions

I'm looking at R/C CDI boxes, but they require a Hall Sensor - I've never tinkered with them before, I just know the concept of how they work.

Where would I begin installing a Hall Sensor on a china motor?

Could I just use an SCR instead of a Hall Sensor?


Here's some links.

RCEXL, RCEXL CDI, RC IGNITIONS, RC IGNITION, IGNITION, CRRC IGNITIONs
HobbyKing Online R/C Hobby Store : Hall sensor for CDI on XYZ 50cc-26cc & HP-50 Engines
HobbyKing Online R/C Hobby Store : Replacement CDI for Turnigy HP-50cc CM-6 Plug
HobbyKing Online R/C Hobby Store : Replacement CDI Ignition for RCG 50CC Engines

I actually would need to run a hall sensor - a hall sensor isn't designed to run off current and measure spark as the white wire is designed to do.

A hall sensor tells the CDI where the piston is - either at top dead center, or bottom dead center and delivers spark at the optimal time. If we could actually get a hall sensor installed in these motors, we could open these motors up quite a bit.

Well, I'm not looking at them as a possibility - I'm looking for how it COULD be done.