A team from XL came to MAN from london a couple of weeks ago to study this exact effect on their new 737-900's.
They looked at various scenarios ie. If bags where being loaded from the back at the same time pax where being offloaded, thus what if a kid tripped up at the back on the a/c thus causing a bottleneck effect, what effect would this have on the balance of the aircraft...
They where also looking at the effect what loading passengers and bags would have on the nose gear. As of now, they havent changed their loading procedure, but i have seen additional stickers within the aft hold used to remind the rampers....
would be interested to see the results...
G-STAW