Messiah,
You are way out of line. No Skipper working for a legitimate airline would knowingly take off if the approved loading system indicated he was 400KG over weight.
I know the figure is arrived at using educated guess work and estimates, but it is APPROVED guess work and estimates, and the figure that is arrived at is what is legally held to be the actual weight of the aircraft.
If you are ever tempted to ignore this, bear in mind that 1) you are breaking the law and 2) if there is any mishap during the flight, even if it is unrelated to the weight, you will be hung out to dry and looking for a new professtion.
I be interested to know which "Brave" airline you are refering to, and how much they would appreciate you revealing that they flought the law on a public website!!