According to discussion in another thread, Protestants (following Luther) do not hold the Septuagint in high regard, compared to the Masoretic text. My protestant bible notes refer to the LXX quite frequently and it's consulted a lot by the translation teams. Couldn't it be argued the Papal church equaly doesn't hold the septaugint in high regard? Thy've accepted some of the books found in the septaugint but not all of them, for example first esdras, the prayer of manasseh, psalm 151, third macabees, The Eastern churches accept these books, but even they relegate 4th maccabees to an appendix and don't consider it scripture. So it seems to me that none of the three main branches on the church accept books as canonical merely because they are found in the LXX.