George, that's a fantastic writeup of old papers - thanks very much for the link!
www.notesonphotographics.org which I would recommend instead of the print addition. It is available on the site as an interactive document plus as a pdf which can be printed in book format.
There is another post here that my book is only about Kodak papers. That is correct in the specific. However, there are some things that are similar in the industry. Regarding papers that could be folded without cracking, the Kodak papers that were advertised for folding were indeed lightweight but the key was that there was no baryta coating -- that is what cracked. Other manufactures used this same process for folding papers.
I'm going to try some this evening just to see if it is any good after nearly sixty years of unknown storage conditions.