And here's what happens.  If I don't use IDL the transmap renders fine and the bangs are gone.  

Now, with IDL during calculation I can see that the whole area of the bangs is calculated and is black with the red dots.   When it renders it's not fully transparent and the forehead as you can see is a darker colour. 

I'm really at a loss to explain this so I'm hoping someone can shed some light.  Please, before I pull out all of my hair :)

Thanks!