why waste your time? i just completed my first arf and i plan on building more so invested $30 on great planes' cg machine. its pretty dead on as far as cg goes. it even has little rulers so all you do is set them to the planes specs, put the plane on the legs and there are little posts in front of the ruler that just touches the leading edge of the wing. plane dips forward- nose heavy, backwards- tail heavy. you can adjust your weight while your planes on the legs. just be careful and ALWAYS keep the plane within hands reach- if its bumped or if it dips, it may fall off. my 2 cents cory