Thanks for your encouraging comments, byRo! I am going to pursue this line of investigation! I have in my backlog of projects a huge panoramic picture from the 60s of my old school. It was rolled up and put in a drawer and (you guessed it) got flattened over time, and now has creases going right through some of the pupils. One of them is me, actually! This is a labour of love of course. I wanted to do it years ago, but did not know the techniques back then to tackle it. I feel like I've learned a lot through this project (every picture restoration is different and pushes us to find solutions, doesn't it?) to pick it up again with a few more tools in my toolbox!
Anybody else want to comment?