ServiceStack Authentication Return Custom Response

Question

I'm implementing a custom CredentialsAuthProvider in ServiceStack and it works great. My only problem is that I would like to return more information back in my AuthResponse. I'm using the following override to authenticate in my custom provider:

public override bool TryAuthenticate(ServiceStack.ServiceInterface.IServiceBase authService, string userName, string password)
{
    // Authenticates user and adds values to session
}

The response I get after successful authentication is the out of the box response that the Auth plugin provides. Is there a way to add more values or to customize the response upon successful login? I don't see any overrides that would allow it.