Custom Renderer using a Border on Windows Phone

I have a custom control BoxViewEx which extends from ContentView to provide rounded corners. On Windows Phone, I have a custom renderer which uses a border control. When I set the background color on the border, the child view isn't visible, I assume because the native control is drawing over the top of the child.

So in the following example,

var page = new ContentPage {
Content = new BoxViewEx {
Color = Color.Red, // this maps to the BackgroundColor on the Border
Content = new Label { Text = "Hello" }
}
};

The label is not visible. If I don't set a background color then I can see the label.

What order do the controls and the renderers get rendered and is there anyway to control this? Currently I have to place both controls and the same child level inside a grid to get the desired result.

Thanks,
Cain