Invisible Helmets and Shots to the Eye

[WhiteLily]

Dungeon Fantasy Magic Items P. 47 gives us "Invisibility...By the piece: The enchantment makes the individual piece (helmet, single glove, breastplate, etc.) making it invisible."

In my game, the majority of kills are from shots to the eye. So I think a helmet featuring a full, invisible faceplate would be something a BBEG would routinely commission.

The armor table on Adventurers P.109 gives the Heavy Plate helmet as 6 pounds plus an optional 2.4 for the (Full Face) and gives DR 7.

Therefore, shots to the eye would still be allowed as they could be seen through the invisible faceplate, but the eyes would now have DR 7.

Adventurers P.109 says that you can still get to the eyes by targetting chinks in the armor at -10, but I'm assuming this would not be the case if the armor was invisible?