Previous theory was that FSD injection functioned as a multiplier to the optimal mass stat. Experiments with Guardian FSD Boosters indicate that in fact it is a simple scaling factor applied to calculated range.
Support Guardian FSD booster.
Use -B/--range-boost flag to set a bonus range, eg -B 10.5.
Maximum laden range of the FSD, including reserve tank, is boosted to the value of the bonus stat by tweaking the fuel multiplier. Consequently jumps of less than the new maximum range will be more fuel efficient.
Range boost is applied before FSD injection and supercharging.