well to answer my own question, I have made a change to the MathUtils private static Matrix3D GetWorldTransformationMatrix(DependencyObject visual, out Viewport3DVisual viewport) method.
Look for this statement:
if (!(visual is ModelVisual3D))
and change it to:
if (!(visual is ModelVisual3D) && !(visual is UIElement3D))
So anything that inherits UIElement3D will work...like ContainerUIElement3D