I believe that weight you have for the OS46 is without the muffler. With the muffler I think it is about 16.5oz which is real close to the Saito 72 at 16.6oz. I use the Saito on my fun fly airplanes because they have alot of torque and can swing a much larger prop. If I were you I'd try the OS70FS. It's a little heavier than the OS46 but you should get more enjoyment from it. If you could get a hold of a Saito 72 then were talking... As for the extra weight 7oz is alot when were talking about a 4-4.5lb plane.