As TreeHugger says, it is all conjecture by those of us creating FMS models.
With the FMS 2.7 .par file, a lot was hidden. Much more was exposed with FMS 2.8 .par file.
Study the .par file to get some ideas of how things work. FMS 2.8 uses an auto mode for wings which divides each wing into 4 sections and calculates the effects of those sections using a single airfoil POLAR. You can use the manual mode to assign each wing section a specific airfoil POLAR.
Of great help for digging into the .par file is Mr. Masuoka's ParEdit program. There are several side calculations he uses to show how he derives .par file variables.
We suspect that FMS calculates all the vectors for specific components and then sums them to get the correct position and direction for the model at any given time. Of course, I could be wrong too.
-- ggunners