Why not just put a "normal" size engine (normal for the plane size, that is) there and just throttle back? You could just adjust your throttle EPAs to give you somewhat the behaviour of an underpowered aircraft. When you get bored (and you will ) just crank up the EPA's and have fun.

That way you could have your challenging "on the wing" airtime and the fun of a basic aerobatic aircraft just a couple of servo blips away.

"Scale" take-offs with 25% throttle can be challenging and fun, but barely flying for 30 minutes could make you fall asleep at the controls.

Joseph