If you are just shifting your main frame/window, I would recommend the overloaded API command. It is SetSimpleAnchor. Then you only have to worry about the parent window and the screen coordinates.
SetSimpleAnchor protected-attributes (object anchorTargetControl, number offsetX, number offsetY)
i.e. frame:SetSimpleAnchor(GuiRoot, 5, 5)
--halja