lol. No one wants to be me when they grow up.
Yes, a bigger dowel would probably last longer. I am using about 3 inches of 1/4" oak rod dowel now. I cracked one or two of the dowels in the last book when I was hammering the tacks in without supporting the piece properly.
For deconstructing purposes here are the rough plans I have developed so far. They are still a work in progress. The pain has been to line up the drill hole so that the book opens correctly but also remains flat when opened. I am rounding only one side so the square sides support the book laying flat (or that is the plan anyway...hit or miss so far). I made a jig to line up the drill holes but still not very precise.
Leather really softens up the books and makes handling them almost a treat. I have a Tandy leather down the road and its been fun re-learning working leather. Highly encourage using for this project.