The RPM figure I gave was for the particular prop suggested for the 3W 24.

I fly 3D with a YS 140 DZ on a plane that weights 11 lbs. It spins an APC 18x8W at 8400 RPMs. I think I could use more power in my plane so that is why I said 9000 RPMs at least for that weight.

BTW I perfectly agree that top RPM does not have much to do in 3D but top RPM on a particular prop does.