Sir George.
The engine is cooled with 'evaporative cooling'; as the coolant evaporates, it is vented out, and lost. So there would be a loss of mass associated with cg also? I believe the evaporative cooler is behind the cockpit, so would this serve to improve the aft cg? Assuming there is always liquid to cool the engine, the mass of the coolant (Water/Methanol) would diminish from behind cg?