Splop and flow along the surface precision

Hello everyone,
I am trying to use the funtion flow along the surface with precision, but the curve gets bigger than the original. I have seen that the more control points the better acoplation has. I need that the original and the new piece with the same dimentions.
I have also try splop but the further from the point choosen the smaller it gets.

Is it posible to use with precision or another function that fits better what a I need?

Thanks in advance,
José Verdú

surface.3dm (1.5 MB)

hi, check rigit, or both surface need to be same dimensions…