Originally Posted by JollyPopper

I assume you are new or relatively new to RC and the answer to your question is so obvious it has us confused. A .40 size engine works well on a 40 size airplane, a .60 size engine works best on a 60 size plane and a 1.20 size engine is recommended for a 120 size airplane. That is not intended to be a smart ass answer, but it sounds like it its.