Investigating X-Wing (OPT and XWI file formats)

The other day I was reminiscing about the old PC games I used to play back in the 90s when I remembered the Lucasarts classic X-Wing. I remembered that in the late 90s I used to make levels for it using an editor. A bit of searching found me two different editors that I remember fiddling with, one was the DOS based "X-Wing Mission Builder" and another was the Windows based X-Ed.

I found downloads for both (the X-Ed website still exists!) and both ran fine on my Ubuntu PC (XMB using DosBox, X-Ed through Wine). Little did I know that these downloads were going to start a chain reaction that would drive me to spend hours of my weekend staring at a hex editor. :)