Am I missing something? Do I need to get my coat?
Too messy..
A stopwatch started at brakes-off and speed check or two should do it - as long as you exclude the use of calculated weight for those figures, so they should be ballpark
minima based on runway length KISS
There's probably a dozen ways to catch this, as a final backstop, including better SOPs when Flex is set.
In this case I'd say the laptop calculation check routines were crap, and not progarmmed by an aviation engineer who'd have all the 'what ifs' well lined up before coding a single line!