Has anyone ever tried to get Active Directory authentication to work for DNN when using two Active Directories that have a one-way trust between them? 

I'm setting up a corporate site using DNN that would be accessible to employees and to alumni, and I'd like to authenticate both using Active Directory.  The Active Directory within the firewall would authenticate employees.  We'd add a new Active Directory in the DMZ and store user accounts for alumni in it.  Then set up a one-way trust relationship between the DMZ-Domain AD and the CorpDomain AD.  The DNN site would live in the DMZ.   When a person hits the site, the DNN site would first ask the DMZ-Domain to authenticate.  If the account is DMZ-Domain \ Alumni1, then they get authenticated.  If the username is CorpDomain \ Employee1, then  the CorpDomain AD within the firewall through the one-way trust would authenticate.  Integrated login is turned on. 

I've gotten most of this prototype working, but I've run into a problem that I haven't been able to figure out.  

• I'm successfully able to login as DMZ-Domain\Alumni1 by typing my username and password using Windows Login on the login page.
• When I try to connect with my employee account, and use the WindowsSignin.aspx page, and type in my username and password into the IIS prompt, I get logged in successfully as CorpDomain \ Employee1. 
• When I try to type in my CorpDomain \ Employee1 username and password into the Windows Login screen on the login page, the authentication fails.  There's a Login Failure exception in the Event Viewer, but no more information than that. 

Is there something different that happens between using the IIS login of the WindowsSignin.aspx page vs typing username / password into the Windows Login box on the signin page?  Is it even possible to use the one-way AD trust idea to get this structure to work?   

We're using DNN 4.9.3.  In the Active Directory settings, it's enabled, Provider is ADSIAuthenticationProvider, and Authentication Type is Delegation.

Thanks!