Maybe I took you too literally. "Ellipse" is a very specific shape, and like I said, I don't know of a way to make it expand. But there are related shapes which aren't ellipses but expand more easily. For instance, consider a table top which is essentially a rectangle in the middle with half-circle pieces forming the two ends. Maybe that's close enough to an ellipse for SWMBO. The nice thing about this shape is that you can put rectangular leaves in it to expand it, and they fit nicely with the not-expanded table shape.