Fuel in center tank may have a serious effect on CG.
this can be a concern for swept wing aircraft (or any aircraft with tanks distributed longitudinally) if you are forced into a non-standard fuel usage pattern.
MEL ops procedures do not apply when airborne.
.. but the wise pilot will use the MEL as a guide to those matters which might be important to think about.
It's useful to carry a blank loadsheet in your flightcase.
but, for the fuel scenario, not much use unless you understand the design of the sheet and how to modify the use to account for the non standard fuel scheduling.