After thinking about this there might be a way to get you kinda close.

Assume you start with a 1 unit radius circle extruded along a path.

Now if you select a hull and scale it by <.5,.5,.5> you'll have a circle at that point of approx 1/2 unit radius.

Likewise if you scale a hull by <2,2,2> you have a circle with a 2 unit radius.

You'll just have to compute the ratio relative to the initial circle at each hull.