Another easy part also is to use a slide switch on the throttle with an override so at half throttle it turns on. Your battery will last a lot longer and it is at idle where you really need the power. I made a lead for Ken from a burnt out plug and a small wheel coller that you insulate with shrink tube. You tighten the allen screw on the centre post. If you wire it in parallel you have the best of both worlds.
Anything that works is all right with me.
John