RE: GP Super Stearman
Aren't they almost the same engine(SPE)? I took my Brillelli out of a Hanger 9 Extra 260. I also have the GP PT-17 and I have a Brillelli GT25(Magneto). Plane balanced perfectly. The 40cc EI weighs 3 oz. lighter than the 25GT(magneto)so it should balance just right.