What happened to @Tsai_totoro 
Going back to the original GH file in the first post, the tunnel sections are defined by sliders that use ‘t’ values, and more oddly, 1 is subtracted from all the slider values:
I’ve considered that a bad practice since my early days with GH because ‘t’ values change when Fit Curve or other rebuild curve methods are applied. So I’ve modified the code to use tunnel section lengths instead, which don’t change if the curve is rebuilt.
14004_2025Feb14a.gh (39.8 KB)