Neck with a floating jaw?

Hey guys! I have a super quick question. I've basically finished my fursuit head, but I was wondering how you guys go about making necks for heads on a balaclava base with floating jaws? I'm not sure where to attach the neck jaw-wise, as it's a separate piece of foam than the rest of the head.

Kinda like this one that I found on google images that happens to be a post here from Growly. Ha! http://i19.photobucket.com/albums/b181/thegreenmooseofdoom/subbyfoam2.jpg