To keep the radar signature low, we use a V-tail on this aircraft. Experience from other aircraft shows that, for stability, the horizontal and vertical projectiona areas of the tail equals the areas from a regular tail, from a stability point of view. These areas can be calculated using the ``volume'' formulas, e.g.
We just project this areas on a plane with 
angle (the angle of our
tails) to get the reference area of the tails.