General questions about deriving from Window

I've created a class that derives from Window, in my solution I have the new class and a demo/test app.

I've gotten most of what I want to do - all of the override logic is coded in the class, the only XAML is in the test app which uses the new window class.

However I'm at a point where I think my derived window class should "wrap" all of the user's XAML inside its own WrapPanel.

Whats the best way to code this?

Can I do it all in code? if so should I do it in code?

Should I create some XAML as part of the new Window class itself, if so how does one acheive such a wrapping? what would be the minimal XAML or must I copy the entire existing Window style before I start?

Thanks

Cap'n