Quick head/jaw question

When most people have a moving jaw that moves as they talk (aka, sensitive movement), what is their starting head material?

Right now I'm building my first "fursuit" (it qualifies, though I can see some fans of the show this character is from arguing against me), and the head is all foam. I'm pleased with how everything is turning out, except that I was hoping to incorporate a moving mouth... if possible, though I get that it might not be.

The foam is flush against my face, and I'm wondering which would be the better move: to attempt adding in foam (and some elastic) to get a moving jaw that would move when I speak, or to just have an open mouth for air flow and if (rather "when," should it not look/act as I'd like) I remake the head a different way, to have a moving jaw on that one?

Also, I'd like to share either progress pics or a video of what I've done, but since this character is very definitely copyrighted to Warner Bros and could almost be considered one of their mascots, would that be over-stepping my fandom bounds? It's a personal costume for me (and will NEVER be sold), so I think it's okay, but I'd rather not get anybody or this journal in trouble.