There were sooo many issues with the construction of this. Even though I did a mock up, first in masking tape, then in craft foam, I did not sew the entire mock up together, but instead, decided that I could estimate a half mock up.... in the end, the mask was significantly smaller than anticipated and I had to do some extremely creative wetform/stretching over the original head bust. This involved soaking the crown/skull in water, but avoiding the molded brow and using all of my strength plus that of my sister to pull it down over the mold wrapped in cellophane.. then wrapped in a couple of diapers for padding.
In the end it worked out, but word to the wise... never take short cuts when patterning. Every project is a learning experience eh?