When I balance my spinners I balance the backplate and the cone seporatly. First balance the backplate and get it as close to perfect as poss, then make an index mark so the cone always goes on it in the same position. Install the cone on the backplate and balance. To balance the back plate I use a drill to make dimples on the plate to lighten, I do not drill all the way through. For the cone I use a dremmel and remove metal from the inside of the cone.