I agree with that assessment. I had to enlarge the center hole in my Zinger propeller to 10mm. Later, I bought an NX Propeller from Airwild Hobbies for just a little bit more. The 10mm hole was already drilled and it appears to be of much nicer quality.

http://www.airwildhobbies.com/MoreIn...t&level=2&id=7

Drilling out the center hole wasn't that hard, but I had to make sure the hole didn't wander while drilling. I used a stepped reamer in my drill press and then followed up with a 25/64" fractional drill (I didn't have a 10mm drill at that time). Then the raised portion of the DA-50 drill guide didn't quite fit into the hole since 25/64" is .390625" and 10mm is .3937". Finally got it all to work after buying a 10mm drill.