If you are using a 2 stroke, you will most likely need a Pitts muffler. One other thing I did was move the throttle servo to the opposite side and had to use a flexible control rod for it to get around the fuel tank. That is all I have come across so far. I am VERY happy with the quality of this ARF and I would bet these modifications are due to me using a 2 stroke. I have another one coming (this one was damaged enough in shipping for UPS to replace it but not so damaged it could not be fixed). I figured I would get a feel for the plane with this one so when I get the other one which will have a YS 63 and digital servos, I will be ready for it. I am also thinking of re-covering the new one. Good luck with yours.