It sounds like it was a real emergency re-design so I guess it's not that odd that there isn't much documentation, it could have been over a weekend. (I drive by the crappy old ILM building all the time and it's amazing what a shoestring operation it must have been, it's pretty awesome. One more reason it's such a shame when any of that early Macgyver work is replaced)
http://starwarsaficionado.blogspot.com/2010/08/ilm-classic-image-first-falcon.html