I am looking for a way to take a spline of a specific length, and adjust its shape without adjusting the length. For context, this is for apparel patternmaking, where you have a roundish armhole shape into which you need to fit the top (cap) of a sleeve, which generally has a bell-like shape. The length of the armhole determines the length of the sleeve cap.
I can draw the cap shape and determine its length, but haven't figured out a way to set its length and keep it constant while I fiddle with the curves. Is there a way to do this?