How does the centre of gravity effect true airspeed?
An aft center of gravity reduces the down force of the horozontal stab, decreasing the amount of lift the wing must produce (conventional aircraft), allowing for a smaller angle of attack, reducing induced drag and frontal area, leaving more power available for pushing the airplane along, giving a higher speed. Alternatively, it allows for a smaller fuel burn at the same speed. .. In the military we would maintain the CG at the aft end of the limit by controlling the fuel tanks we used first. It results in less stability, but nothing the autopilot or even the copilot couldn’t handle. We would shift the CG forward during inflight refueling to improve stability and handling, and then move it aft again.