You can position the `RectangularCoordinate` used in that chart appropriately to fill up the whole space. (`CoordinateSystem` determines the size of each chart rendered within the `SOChart` component).
RectangularCoordinate rc = new RectangularCoordinate(...);
Position position = rc.getPosition(true);
position.setBottom(Size.pixels(0));
position.setTop(Size.pixels(0));
position.setLeft(Size.pixels(0));
position.setRight(Size.pixels(0));
Instead of setting them to zeros, you may have to give certain amount of space for the labels. You will be able to figure it out.