Sky Captain
Right. fwd cg difficult to raise the nose; aft cg difficult to lower it, all related to the distance of the cg from the tail. The key is the discrepancy in up or down authority, as the cg moves in relation to the control surface necessary to rotate the mass. The tail is necessary to balance the airframe. Disregard the cg. Think of the Lever. The cg is the fulcrum. Nose and tail are either end, move the fulcrum and gain an "advantage". The warning to everyone is this: when the force necessary to move the nose up or down differs by more than a little bit, you are having cg issues.
AF
Mark - The difference in cg isn't so important as the Physics when it changes. I'm the only one?