After several attempts, it became clear that an array of spheres centered on the radius curve has an envelope that is larger than that of a swept vertical circle, as described in the previous post.

The previous post was modified to correct mistaken understanding.

So I will have to find some way of finding the envelope of an array of spheres centered on the radius curve, with decreasing radii.
Maybe with Scaling the array of spheres with coordinate values of points on the radius curve, and then ???

There might be some kind of formula or moving frame???

- Brian