I would like to meet the people who determine proper engine size on ARF's etc.....I bet they all drive 4 cylinder econo boxes and mini vans. My Super Stearman 40 calls for a 48 to 53 4 stroke. I put a Saito 72 on it and it's just right.
The Super Sportster 40 is a dream machine with a Saito 72 as well.
In my opinion; Add about 20 to the highest number they suggest and your plane will not only be more fun to fly, but, you'll also be able to get yourself out of trouble when needed.
Theres no substitute for hosrepower in a stall.
Dennis (Red Bluff,ca)
Real airplanes have 2 wings and round motors................