Well as best I can gather there are two types of prop hubs or shafts for this conversion. The first is a hub that you would use with the stock flywheel. It really dosent work without the flywheel so it is nessacary to macine down the stock flywheel hub to match the prop hub to be able to get a spot to mount the magnet. This is the type I have as i bought a paragon aeronutics conversion kit and the project got benched for a few years. Paragon has since gone out of bussines as the owner has died or so i have heard. As far as where to put the magnet it should go near the same spot as the stock magnet. the hall effect sensor is ussually held to the output shaft housing with a hose clamp and will be now well exposed after machining down the flywheel. if The magnet is located in the same spot as the stock magnet and the hall effect sensor is mounted in the area where the old ignition coil was located then it should all match up pretty good. As far as adjusting the timming of the hall effect sensor it is ussually just rotated on the shaft housing.

The second type prop hub is used without the flywheel and already has or has a spot for a magnet. I have not seen one of these as this is not what I have.

I will be covering this conversion on the ignition on the another darn ryobi post that I have started when I get one of these units.