The Devourer - building up

Even with the legs filled with Plaster as they are, there's no way they'd support a body that bulky made out of solid clay.
Would be real expensive too.
So, i need to bulk out the form first.
To begin with i attached a piece of card that roughly gives me the height i need to build to, and an idea of where the open area will be:

After that, i'm adding balls of rolled up Bacofoil, holding them in place with various tapes: