I would say the somthin extra also. I am currently building one of these. A guy that I fly with has one with a Tiger .46 on it and it has plenty of power to do anything he wants to do with it. Just don't put the tires from a r/c monster truck on it like he did. It flew well until he tried to come out of a torque roll and the plane stalled and crashed. No major damage though just broke the landing gear off.

Chris