Ive got a ST .61 and the only thing i did was put the battery a little twards the rear. LOVE Mine. I am going to glass over the landing gear to make it stronger. my fuel line was bad and fuel soaked the whole area inside and it took a bad bounce on the third flight and broke out the gear. such a nice plane! I dont know if I would recomend the engine to airplane combo. go four stroke like a os 70. good day!