What fuel are you using in the engine. If it is knocking from detonation, it sounds like your fuel has too much nitromethane in it.
i would try some 5% and see how it goes.

I am still running a old SAITO 80 with high compression and it liked 5% nitro glow fuel just fine. It has never had any of that special 4 cycle fuel in it. Just regular airplane fuel with a blend of synthetic and castor oil.

My old OS FS91 Surpass liks 5% just fine too.