Many old Bibles and other large books may benefit from over-sewing (or over-casting) the shoulders when being repaired or re-bound. This technique strengthens the shoulder area, securing the first few sections as well as potentially securing the cloth joint and, in this case, the board attachment cloth. This may not be appropriate practise in a conservation sense, and I would be unlikely to use this on very valuable or historically significant volumes. However, many larger books over the past couple of hundred years were over-sewn for added strength and this can commonly be seen when repairing these books. You can refer to Bernard Middleton's book 'The Restoration of Leather Bindings' (page 94/5) for more information.