Not sure if you wonder if the engine is too small or the plane is too small for the 1.20 engine? The plane is slightly smaller then my CG Extra and I fly it with a 1.20 YS four stroke and have even used the OS 1.20fs. Today you can even use the 20cc gas engines in it.
If you go into the ARF forum you will probably find the plane there and see what others are using and what they think of there combos.