With the square wing you can easily calculate the CG. Measure the chord and start at about 25% x chord back from the leading edge. Then move it around untiul the plane flies the way you want it to. Don't trust the CGs in the manuals. I don't know where some of them come from, but they can be way off at times. Always calculate the CG or use the conservative side of the manual's CG for the first flight. My last 50cc gasser was so tail heavy with the manual's CG it shot straight up when it left the ground. Got real exciting there for a little while. Finally got it gathered up and back on the ground. Needed 14oz. and all the batteries forward to get it flying right.