I am wondering whether "align" attribute could be supported for rectangular elements such as gallery and album artwork. What I mean by that is x and y values of those elements are, by default, of top-left corner point. But align="Bottom.Right" could change the base point of the rectangular element to bottom-right corner point. So except for the default top-left, three values (Top.Right, Bottom.Left, Bottom.Right) are possible for the attribute. If this can be supported, we can place variable sizes of gallery and artwork to virtually any places of screen by controlling its aligning point.
With regard to the case above, xAnchor="Panel.Right" x="0" align="Top.Right" will easily solve the problem. Then we will no longer need +/- values.