Thanks Andy for adding your first hand experience. It is interesting that the C7 you mentioned had that kind of head rest armor.
Chris, thanks also for that chart on the Bf 110 G armor. Haven't seen that one before.
In trying to pin down when armor was first introduced, I found this image on my hard drive...unfortunately I can't figure out where it is from (source) or if it is in fact for the Bf 110 C.
Attachment 3246
Still it is confusing as to why there is contradicting information in reputable books.