25 to 30% back from the leading edge at the fuselage is safe for most any airplane. Take that percentage times your cord at that location and see where you are. Nose heavy is way safer than tail heavy. Your optimal balance can be ascertained in the air with a simple flight testing procedure, but for now, I would use the 25-30%. Nose heavy, you will need a little more speed on final, a slightly steeper final approach, and a more deliberate flair, but you will be perfectly fine. Fortunately, the Sukuoi isn't snap-happy and sensitive to elevator like the Cap is. See how it flies and adjust the CG AFT, 1/4" at a time, till she has a very slow relatively level sink rate, wings level, in a glide, and both right side up and inverted. When this is accomplished, you will be able to slow down and glide in to landing.