I assume you are talking about the indention on the kick panel for the headlight dimmer? I think I would lean toward your idea of sectioning. The only other option would be to beat the indention...and that would likely take a lot longer than piecing it together, and then rounding the corners with a hammer/dolly. Probably best to cut, shape, and fit the sections before you cut out the original, just so you keep your reference as long as possible.
If you get in trouble...let me know, as that section of my donor car is not too bad. I can cut it out and ship it to you.