I have no desire to touch Vehicle Maker, that is Marc's creation. I will just try to put vehicles into it. I already know that I am going to have to play around with the Armor Protection values.
On page 640, one centimeter of Iron, presumably Wrought Iron, has an Armor rating of 50. Mild steel, either for ship construction or armor purposes, was rated as about 30% stronger than Wrought Iron, so should be 65, which is not far from the 70 which one centimeter of steel is rated at. Good quality rolled homogenous armor plate, not face-hardened, was about 2.25 times stronger than Wrought Iron, with face-hardened plate rated at 2.6, although thin face-hardened plate was hard to make and apt to shatter under a heavy impact. One centimeter of plate, or 10 millimeters, was barely bullet proof in World War 2, with most tanks having 25 millimeters of plating as a minimum. When you combine the greater strength of steel armor with a much greater thickness, your armor protection factor starts to take off really fast. Adding slope to that makes it that much worse.
There does not appear to be any provision in Vehicle Maker for the effect of sloped armor plate, or varying thicknesses of plate on a given vehicle. So, the question will be, do I plug in the increased protection from sloping or not?What I may do is put in two armor values, one without slope and one with slope, or simply use the turret value for armor protection, as there is no way to distinguish where the varying thicknesses are.