@ Totto,
just for your reference, I flew a Hanger 9 Corsair with the Saito FG84 and a 3 blade scale looking prop like you have there on your build. I just wanted to say the engine was not loaded properly and it flew poorly as a result. The top end RPM was high and the plane flew slowly because the pitch was too low. Landing the plane required a high throttle setting, etc..
I’m just saying check the engine is pulling hard like a 24x12 prop would do. I’ve tested the FG90 with a 24x12x2 blade on the ground and the RPM was right on target.