Here you can see how to shorten a curtain panel from the top. This particular panel had a lovely add on panel ‘extension’ at the bottom which my client wanted to keep, so I shortened it from the top. Some hand stitching was involved to replicate the original work exactly. You can see the white buckram stiffening in the top image. Using this gives a lot of flexibility for where the curtain hooks are attached. They can be positioned to either hide or show the curtain rail or the rings they will be attached to.
The Cycling Curtain Maker 