Before doing anything else, I decided to reinforce the board attachment. The boards were still attached by the original cords, but one was broken and one was loose. I laced some Irish linen cord through the original holes, top and bottom. Two of the old cords were strong enough that I felt comfortable knotting the new cord to the old, and two were weak enough that I laced the needle through the back of the spine. I adhered the new cords to the top of the new spine with PVA – it doesn’t cause the linen to swell the way paste does, and since it’s new to new material I don’t worry about reversibility.
I have a plan to fabricate the new spine in such a way that I can decorate it off the book, and do it over if I mess it up. More on that later.