Squidlord
The answer is (2). What I am not sure is if they have been used because:
a. It is a documented number that they can stand back from if it goes pear shaped.
b An assumption because no other data was available.
c. Because it makes the safety case add up.
d. Its too expensive to come up with their own data for that particular situation.
That said I am not sure that it is a solvable problem until you have fleet data to work form.
regards
retard