Offset 3D Curve

I try to move the outlines of my T-Splines surface / brep 5 - 10 cm inwards to extrude them and generate a railing for my surface.
Unfortunately, neither offset nor offset loose does work at all.
I hope you can help me.

Regards Phil01.3dm (313.4 KB)

In this case, “Offset on Surface” doesn’t work very well as expected, BTW, there is a workaround…
Take a look at the attachment. (98.9 KB)

1 Like

Looks very good and also very close to what I’d like to achieve.

Is it also possible to get only the outer contours of the surface as a closed offset instead of each one?
If necessary, I have to remodel the last edges by hand.
Thank you very much!