WIP First Fursuit Head, Lower Cheek Placement Issues

I am about 75% done with the foaming stage of my first fursuit head- I just have to fix some symmetry problems, shorten the lower jaw, blend in the eyebrow ridges with the cheeks, make the ears, and make the nose. He is a red panda.

However, as you can see from the pictures below, I need to add foam underneath the already existing piece to complete the cheeks, flesh out the face, and enhance the expression. I do not know how to add a piece or what kind of piece to add without impeding the movement of the elastic when I move my jaw, if that makes sense.

Center:


Center Angled:


Side Angled 1:


Side Angled 2:


Full Side 1:


Full Side 2:


You can view my concept art at http://fursuit.livejournal.com/6296215.html

...So, how exactly am I supposed to do this? If I added foam down there and blended it with the top pieces, it would eventually rip (or just look strange under the fur) as I moved my jaw, right? I've already done a lot of research and haven't been able to resolve this. Perhaps I'm overthinking it.

Additionally, feel free to point out any mistakes I've made. How does it look so far for my first head? (Aside from the symmetry problems I already mentioned)

Thank you for taking the time to answer my question.