It only work on XZ plane… But it is simple to change the plane.
You don’t have to transform your curve to polyline. As I had not your plugin I used textObject from Rhino. Spiral.gh (16.1 KB)
Here I drew a spiral in rhino -since I don’t have the gh component that you use- and wrote a gh definition to scale it non-uniformly. Narrow on the bottom, large on the top as you pointed out on your image.
You can control the uniform scale by creating a surface from two circles and use pull curve, in the definition other method to create the helix helix_2.gh (18.8 KB)
Really appreciate your help but I am afraid I still did not manage to do it.
I am attaching a better explanation.
I would like a non uniform scale on the y axis which will gradually get less on the lower circle.
I am attaching also the component I use for the spiral.