@Pilou,

re:
> Seems do not working with a start rectangular surface & a curvated rectangular surface as target! ???
> Makes nothing!

See my above reply - if you turn on control points for your 2 surfaces using Edit > Show pts you should be able to see that your curved rectangle is a trimmed surface with the same underlying surface as the start rectangle.

Since surface to surface flow works by using the underlying surfaces that will produce no change since it's mapping from one straight rectangle to another straight rectangle.

You need to use some other construction method for making the curved surface, not Construct > Planar. You could do a loft between the 2 curved pieces, sweep using the curved pieces as rails, or Network.

- Michael