Sidebar layout under uneven heights

The sidebar layout with one side much taller than the other, which is the only time the grid placing its regions shows what it does with spare height. A long body beside a short column should leave the blocks of the column stacked at the top of it; a tall column beside a short content region should not hold the next section of the page away from the content. The regions are outlined -- content blue, sidebar green -- so that a gap is an empty box rather than white page.