What a great story! Find some period photos is my suggestion. They carried all sorts of things on those roof racks....
Here's a 4CV in France just last year. Fishing tackle on the side and anything else on top.
Is your car before the time Peugeot had built-in roof rack mountings?View attachment 121704
I have plenty of period photos - everything from artillery shells to gas converters were mounted om them. I started a Facebook group for theses cars and it's amazing what photos show up! There are no permanent mounts on the roof. There was factory accessory rack but I'm not sure how it was mounted.