Hi Chris,

Yes, it is possible. You can obtain the UXFrame element by inheritting the UXNavigationWindow class, and then access the "Navigator" property in OnApplyTemplate method which you need to override to configure more settings on the UXFrame.

However, be warned that INavigationContentLoader is Silverlight 4 specific API. It's not supported in SL3, WPF 4, nor WP7.

Do you have any specific scenarios that are unsupported in current ClientUI navigation framework?

Actually, here is what I'm doing:

1. First, I created my own implementation of the INavigationContentLoader.
2. Next, I created a Xaml Style for the UXFrame and set the ContentLoader property to my implementation.
3. Finally, I set the NavigatorStyle to the style for the UXFrame.

Now I can step into my custom content loader and handle loading of navigation items according to my custom implementation.  I'm not using the application framework the way the ClientUI does.  I have my own Prism based solution.  I'm tracking all of my application instances in a custom application manager and that ultimately serves as the data source for my UXDesktop.  My application is strictly limited to SL4.  We may modify it in the future for WP7, but that won't be for some time and will likely not include the desktop paradigm (which uses the custom navigation). 

I actually ended up going with this solution so that I could allow developers creating apps to run on my platform's virtual desktop to specify their own INavigationContentLoader for the UXNavigationWindow.  Now, one app can launch a UXNavigationWindow and use the default behavior for navigating, while another app can impelemnt their own way of handling navigation within their window. 

I just added an INavigationContentLoader parameter to the constructor for my custom UXNavigationWindow.  The I set the Navigator.ContentLoader property to the value of the parameter.