Posted for es39wg@comcast.net:

 
 On one of my planes, two blades, the tech tried several times to balance the
prop with an accelerometer at the front and back of the engine.
 The computer kept telling him he didn't put the weight in the right place
each time he added it.
 After he got it as good as he could, and neither of us happy, he measured the
prop shape from hub to tip.
 The blades didn't have the same twist. After I flew it, I decided it was good
enough for now, much improved. High time engine.
 And yes, he attached the washers and screw to the spinner backing plate.
 Please, do not add to the starter ring gear. You will eventually regret it.
 duane N39WG Golden West Grand Champion winner