[lch]

Head protection is counted as 20% towards final protection when that is being displayed on the unit infoscreen. Hit probability is the same, I'd think.

Originally there were more hit locations than head and body planned: arms, legs, and so on, and the armors in the game still have values for those parts, but in the end those values are only entered into a formula that determines the resulting body protection, they're not being targetted directly and protected individually, AFAIK.