So here are some reference pics based on Iriorne's measurements. There are a couple of problems that I see:

1. With the head at this size, the ears are about 1.5 - 2mm too wide.
2. If I reduce the size of the head to accommodate the ears, the head looks too small for the model.

I might try reducing the "ear" size and making them a bit thinner, that way I don't have to reduce the head size too much.

I still have to reshape the back of the head to square it off for the ball socket section. Shouldn't be too much of a problem. I think I have an idea of how the ball socket is going to work, hopefully it comes out alright!

Any other thoughts or suggestions to make this work?