Alan,
Believe it or not, I assumed correctly how you intended it to go on. I for some reason thought it would be easier to add the ear base and back as a first layer. Clearly not the way to go.
I think one piece will be best, and what you descibed is exactly what I will do. One layer all the way around first. The I'll cut out the cheekbones. Then, wrap a second slightly larger piece around that to form it. Remove second layer, cut out rear section and cheek bones. Attach over first piece. This will give me the raised brow, and raised ear bases.
I think I'll trim the visor slot on the interior piece slightly larger than the exterior one. That will give me a good lip to mount too.
We'll see how it goes!