I would think it would be tough to get an accurate calibration, depending upon the variability of your flights. The FF sensors work by sending an electrical pulse each time a pre-defined, amount of fuel flows through it. The EMS simply counts the pulses and turns that into a flow rate, based upon the # of pulses per second. The calibration is used to tweak the association between electrical pulses per second to actual GPH displayed/recorded.
An EFI, adjusts fuel flow by changing the amount of time that the injector is open (the amount of time, in microseconds, that voltage is applied to the injector) . If you assume a constant fuel pressure, you can calculate fuel flow based upon open time. However, it is not constant. During the initial time that the injector is opening, the flow is different than when it is fully open. The bigger issue is that the EIS is using the number of electrical signals per second to create a fuel flow. However, in the case of an EFI, each electrical signal from the injector is not representative of a static fuel flow. You have to measure the length of the electrical signal to capture fuel flow. I am sure this is why it took Ross some time to write the code for it. It is not a simple activity.
Larry