The doctrine of _sola scriptura_ is not really about 'which books' but about the ground of authority--is it in God or is it in men? Do the Scriptures create the church, or does the church 'create' the Scriptures? Does the church recognize and receive the inherent and self-attesting authority in the Scriptures, or does the church 'bestow' its authority on the Scriptures? The Creator-creature distinction requires the former option in each of the three questions above. That's the essence of this argument between the Roman denomination and the Protestant & Reformed denominations. Both sides of the argument make an appeal to authority--but the former appeals to its own man-based authority, and the latter appeals to divine authority. But to your question in particular, I think Jerome had the better canonics (vs. Augustine) even though I tend follow Augustine's soteriology (contra Rome, which returned to semi-Pelagianism centuries ago).