RE: Variable CG?
I guess you are not familiar with those planes. Look at the landing gear of the F4U Corsair, for instance. When the wheels are down, they are under the wing leading edge and ahead of the CG. When the wheels are up, they are back near the wing trailing edge and behind the CG. Those are heavy wheels. I should know because when I retract the wheels, the plane becomes slightly unstable and twitchy.