iControl Rest Api Authentication/Authorization with Active Directory

I've been trying to get something like this to work for my customer, with no success. I tried manipulating the Authorization header, keeping BigIP credentials and AD credentials the same, but while my logic appears sound, I don't think the BigIP is allowing me. I'm using an APM profile to do the auth, but it's just not yet working. I'll post more on DevCentral later if I get it working.