Shape keying curve object control point radius not working


I’m trying to morph a cylinder into another cylinder with a different location and radius. As I’m going to have a lot of cylinders in my scene I’ve chosen to use curve object (either Bezier or NURBS) with just two control points and the Bevel Object set to a Bezier circle. What I then tried to do was adding two shape keys to make the morph by changing the location and Radius parameters of the two control points. However, while the shape key seems to work for the location, the Radius value of the control points does not seem to get stored in the shape keys. Has anyone encountered this before? Is it a bug or just a design choice? This seems odd as the Tilt value of the control points seems to get stored and can be shape keyed. I tried google and searching BA but with no luck.