Without realizing there was something like a prop reamer, I drilled out all six of my new Graupner 9x5s, using the 8mm step in the prop as a drill guide. Of course I understand now that this is not the correct method, but I can't stand the idea of throwing away $70 with of props. The chance of getting an eccentric hole would be greater if you start drilling from the small end, but then if you don't touch the 8mm step you are still good - I didn't do that either. For what it's worth the holes look perfectly centered and the hex flies great. I'll buy a prop reamer for next time.
Also, as most everyone probably knows, you have to use a washer when using the Graupners. I did notice that some people were putting the washer on top, which I think is a mistake. An 8mm washer won't center properly on the less than 8mm threaded shaft. and a less than 8mm washer won't put pressure beyond the threaded portion, which is where it is needed if the washer is on top. With an 8mm washer on the bottom, it will be centered, and it will push the prop up into the threaded part of the prop adapter. I have some APC's (for another hex) that come with a washer for this reason, and they recommend putting the washer on the bottom. The only downside is that it is harder to tighten the props as they tend to slip on the washers, but I think if you hold the motor and the prop together, you can get it tight enough.
Sorry if this info is redundant.
Russ