Easy question: Scaling pre-made curve to grasshopper made box

Hey I cant seem to solve this simple issues. how would I scale this so the black feather is always the same as the red box. the red box is made in grasshopper and I cannot seem to get it to an object. grasshopper|690x388

Make 2 bounding boxes, that will be flat boxes because your geometries should be flat. (if not, project your geometries first)
And then use “Box Mapping”.
Geometry, the feather curve.
Source box, your bbox from the feather curve.
Target box, your bbox from the red rectangle.

Thank you for your help! I had to use rectangular mapping but i would have never found that. Thank you!