With utmost respect, the .cfg file is a direct function of the simulator and should not require modification to calculate the correct KIAS.
Furthermore, the linear function of an offset and a multiplier fail to accurately model the non-linear relationship as per the Cessna POH, as below:
That said, I am of the opinion that Asobo should focus on accurate flight/atmospheric/world models and leave [accurate] aircraft to third-party development, so it is positive to hear that the environmental aspects appear to be correct.