Hi Nruddock, I missed that thread but is already a while ago. But I think by using a colormath node and the eyedropper you can choose the zero level of your displacement bitmap if you have a more complex map than my simple three colored map. I guessed someone has found this out earlier but I couldn't find a reference.
Thanks for the link.

regards,

Bopperthijs

But I have more in a next post....

-How can you improve things when you don't make mistakes?