Okay so the car is raised by 15mm and there is a protective piece fitted to the underside of the body.   My questions are :   1)  While ride height is up by 15mm, does this actually mean the distance from the protective piece to the ground is 15mm more than the distance from a standard underbody to the ground, or as I suspect, the net difference somewhat less once you take into account the protective piece.   See, one of the reasons to want a higher riding car is I am sick of unreasonable