Moses, that nut adapter would work well. I have the opposite problem in that the bottom of the nut adapter extends well past the washer, so I don't have a problem using it to center my prop. In fact, I will actually use all the threads on the nut when trying to tighten the prop down, so I got another washer to ensure that the prop gets tightened all the way. Either way, there is plenty of thread for the nut to tighten down on, and the prop is perfectly centered when installed. The spinner backplate was drilled to perfectly fit the crank.

Hilleja, I have not had a problem with the engine throwing the prop unless it is flooded and kicks hard when trying to start it. Then again, I don't try to start it at full throttle. If it starts backwards then I apply a little pressure to the spinner and the engine usually starts turning the correct direction.