Gentlemen, while the more arcane technical details are beyond my ken, I can say that I once was an airline bean counting type of person and I know a lot about cheese paring as we called it, and I used it to great effect trimming maintenance budgets for six years.
We do these little calculations about the weight of oranges, pencils and charts and approach plates, you name it, and then we innocently make the claim that if perhaps, you only carried the approach plates you really neededfor a flight, it would save the company X hundreds of thousands of dollars a year. Our logic appears irrefutable, or appears to be.
However, the logic is flawed because you haven't subtracted from your savings the risk adjusted costs of not having what is required. That was the original point of my post, when I glibly said "take a bit extra for mum".
To put it another way, it was great that I saved tens of thousands of dollars a year by cutting our stock of widgets in half, right up to the day where an aircraft was grounded for three weeks due to lack of widgets wiping out six years of savings in one day - you need to look at your savings in perspective compared to the possible outcomes.
But the more sinister issue is allowing too much "bean counter" influence over operational decisions, because what starts as "voluntary" cost cutting programs have a very nasty habit of becoming "compulsory". Furthermore if you give in to such forces and the operations manual is not amended to reflect them, which it won't be, and you cut things too fine one day, you will be hung out to dry by the authorities.
I guess the simplest thing for the authorities to do is monitor the number of "low fuel" calls, if the number starts trending up, the bean counters have got at you too much. Fuel is your decision. Keep it that way.