Yea, I've tried using the normal method of _window.Get<Control> to find the elements in the tab, but without success.
It is my understanding that
IUIItem items = _window.GetMultiple(SearchCriteria.All);
will find all of the visible items on the screen, then while debugging it's easy to see what items are available, that's why I was using it.
If you can use the normal Get call then maybe there is something strange about my tab setup. I'll try it with a more basic example.