I like the jack-screw idea, but don't like the slow response. I want to move the battery (a sygnificant contributor to an electric plane's wieght) around a little, but not drastically.

I shudder to think of a very rearward CG that cannot quickly be moved forward to save the plane.

I actually want to move the CG aft until the plane diverts, then bring the CG forward and see how the plane reacts (with no control input). It should be an interesting thing to experience.