I seem to recall many many years ago a cargo DC8 went into an uncontrollable climb/stall on take-off at ANC due to load shift. If this was a specialist cargo operation, the crew may be more attuned to the perils of aft loading than you realise. Load shifting is not rare, and it is going to go backwards- if you are really close to the aft limit it's not going to take a lot to have an unflyable aeroplane on your hands! Another incident recently was a B1900 in the US doing the same. Inbetween there have been many many accidents like this. I saw a picture yesterday of the MD11 on its tail- aeroplanes don't like aft cgs though they may save a miniscule amount of fuel.