If I add a side anchorable then a bottom one, the bottom overlaps the side.

---------------------------------------------
|                                     |                 |
|                                     |     Side      |
|                                     |                 |
|--------------------------------------------|
|                                                       |
|                      Bottom                       |
|                                                       |
---------------------------------------------

But if I add a bottom anchorable then a side, the side anchorable overlaps the bottom:

---------------------------------------------
|                                     |                 |
|                                     |                 |
|                                     |     Side      |
|----------------------------- |                 |
|                                     |                 |
|            Bottom               |                 |
|                                     |                 |
---------------------------------------------

I would like to be able to control this so my anchorables will have a deterministic ratio of space.

Is there a way to do this?

NOTE:
In case it is needed, here is how I add my anchorables.  I call this in my ILayoutUpdateStrategy.BeforeInsertAnchorable method.

private static LayoutAnchorablePane AddAnchorable(LayoutAnchorable anchorableToShow,LayoutRoot layout,
   AnchorSide anchorSide, AnchorableShowStrategy anchorableShowStrategy)
{
   var addedToLayout = false;
   if (!(anchorableToShow.IsHidden || anchorableToShow.IsVisible))
   {
      anchorableToShow.AddToLayout(layout.Manager, anchorableShowStrategy);
      addedToLayout = true;
   }
 
   var anchorablePane = layout.Descendents().OfType<LayoutAnchorablePane>()
                                            .FirstOrDefault(p => p.GetSide() == anchorSide);
 
   if (!addedToLayout)
   {
     anchorablePane.Children.Add(anchorableToShow);
     anchorableToShow.IsSelected = true;
   }
   return anchorablePane;
}