7700
Very true but don't omit the extra weight of the crew! Back in 1979 when I joined up I was a stude with a personal AUW of 73 kgs, c. 11.5 stones. Now, though it pains me to admit it, I'm more like 93 kgs or 14.5 stones.
Add to this that all ac seem to put one weight as they age, more layers of paint etc. and as you say minor aerodynamic imperfections it's is hardly surprising that performance drops off.
MB