So to describe an object in space, it requires a certain amount of vectors. It is clear to me the initial hang test is to establish a balance from an point at or very near the place of lift the rotor will be of influence on the fuselage. This is a good thing to do and I have read/heard and therefore understand, a nose down slight angle ( 3 degrees ) is about right. This can also be used to adjust and center the control stick. I could be mistaken. Once this is established and a plum line is drawn, this becomes the first vector. This line is obtained by allowing the fuselage to pivot under the point of suspension. This a Similar point of suspension which the fuselage will be allowed to pivot when in flight. Agreed? If a hang strap is fashioned to where the attached rotor becomes the point of suspension or we could construct something to support all of the lengths of the rotor blades and the entire gyro was lifted from the floor, the first pivot line would be the same. Wither the rotor off or the rotor on be used to suspend, it is the balance of the fuselage which is measured by drawing the plumb line. Now what is the purpose of the second vector but to show where the CG of the fuselage is, after all it will be suspended by the rotor in flight. Adding the tilted weight of the rotor with all of the moment arm involved will not give a true reading of the center of gravity of the fuselage as a component alone. Apples need to be compared to apples.