Just discovered the other day that EFII uses the top dead center hole on a lycoming flywheel to mount the magnet for the hall sensor. Those holes every 30 degrees are the extremely easy place to add weight for prop balancing on a lycoming which forces anyone balancing their prop to then drill holes in the spinner backplate. Propeller balancing is probably one of the cheapest and most valuable things you can do for an aircraft to prevent fatigue damage. IMO, anyone adding the EFII should remove the flywheel and drill a 3/16 partial depth hole to mount the magnet on a different radius so that the pre-drilled flywheel holes can continue to be used for balancing. EFII just uses a dab of epoxy to glue their small magnet in the 1/4 inch hole.
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