Why does Project break my data structure and how can I get it back?

[closedcurve (Weston)]

I’m trying to project these lines onto a surface and keep the structure that controls my line thickness. It works as Lines (left) but not my Curves (right) because the structure changes.

Any idea why or how I can match the original? I tried Cross Reference.

projected lines.gh (92.1 KB)

[HS_Kim]

Use Shift Paths or Trim Tree…

projected lines_re.gh (89.6 KB)

[closedcurve (Weston)]

Thanks so much. Still getting the hang of list management.