Consider -
(a) the practical rule is "don't crash".
(b) the rule following the mishap is "make sure that you have a good story for the Judge" .. as you are going to live/die in your career etc., on the basis of whatever your decision processes were on the day.
Putting whatever rules may exist and whatever your interpretation of the rules may be to one side ... this leads to
(a) if the operation is planned and has available options and alternatives, then adopting not less than the normal certification fudge factors which have stood the test of time .. just might be a good idea as a routine protocol. The AFM/POH is a useful tool in such circumstances.
(b) if time, fuel, location, and system problems dictate that you have run out of the nice options you would have preferred to have had available .. then you do the best you can in the circumstances .. endeavouring to load the dice in your favour throughout. The QRH/MEL are useful tools in such circumstances.
Of course, the question of why you, as Commander, were in that latter situation may arise subsequently .. but one is better served by being alive and having the opportunity to be able to attempt an answer to the question ..
.. as to the strategy of intentionally squandering those fudge factors in other than emergency or abnormal situations .. where one doesn't have better options ... just doesn't bear thinking about.