Armor Penetration Model?

[MarkSheppard]

I don't know, but it always seemed to me that one inch of steel armor = one armor unit

It's actually 1 unit of armor unit = 1 cm of armor.

The Formula to get Armor Thickness with slope taken into account is:

(i'll provide it in MS Excel format to make it easier for youa ll).

Armor Plate Effectiveness=(Thickness / (COS(Degrees from Vertical*0.017453293))

What this means is:
14mm of armor at 50 deg from vertical = 24mm
50mm of Armor at 55 deg from vertical = 87mm
and so on...