ORIGINAL: Richard L.

Most of the weight is in the wheels, just like the weight of a pendulum. The mount doesn't change, but the weight shifts from one point to the next. You might be thinking too hard. The CG is affected by weight and how far it is away from the CG (moment arm). It doesn't matter if the anchor point doesn't move. The strut acts as a moment arm. When the wheels are up into the rear of the wing, they want to tilt the nose of the plane up. Put your plane on a balancing stand and put a pair of wheels on the leading edge of the wing. Now move the wheels back toward the trailing edge of the wing.