I've found that the neck has to elongate to allow it to incline foward and back properly. This gets pretty complicated; it means another joint at the base of the neck, that I have access to when animating. And the head has to be able to move up and down on a rod of some sort. And, I have to be able to tighten the head to the rod very firmly. This makes things a little awkward for animation; I can hardly tighten and loosen the joint for every frame while animating. It will need to be tight, as the rubber mask/neck will be attached to the shoulders, which will create alot of stretchy tension when I extend the head along the theoretical rod.
There's one simple thing i'm going to try; there's a type of electrical wire covering you can buy at hardware stores that is pretty stiff, and bends like vertabrae. I'm going to go look at the stuff before I try to get too complicated.