Hi,

I have found out this engine is a torguer engine and dont like to rev. Mine is also getting 7900-8100rpm on a 18x6w but the interesting part is that it easily turns a 18x8w@7600 and a 19x8w@7000rpm without any signs of overheating or fueldraw problems.
However for extreme aerobatic and 3D the 18x6w seems to be the best prop.
On a warbird i would use a 18x8w or 18x10 and 19x8 for scale planes.