On my Ryobi conversions I took the mag/flywheel off, put a 3/8" hole the length of a piece of 1 inch aluminum stock, made a small forcing cone at the back of the prop drive and put a slot for the woodruff key, drilled a hole to accept the button magnet for the hall effect, then peened the mag in. The first conversions I drilled 4-40 holes (#29), then taped them, but now I just scuff the front of the motor and use a hose clamp to hold the Hall effect sensor on the engine. I timed them so the back edge of the magnet was about 3/8" from the sensor at TDC, then fine tune the timing while it's running.

This all sound hard, but it's quick and easy to do, and you end up with a much better engine.

I think that when you remove the flywheel the engine will shake more at idle, but they smoothen out as you increase the rpms.