I had no idea that the Gloria was added by Louis de Montefort.
Daniel, when you say the mysteries take you 12-13 minutes each, are you referring to the full sets of mysteries (Joyful, Sorrowful, Glorious), or each individual decade? I think you and drummerboy may be referring to different things.
When I visited the SPPX seminary in Winona some years ago, they said the Fatima prayer in Latin, and I was surprised by how little connection it had to the English version.
I don't feel generally opposed to the Fatima prayer, except that I find myself reflexively starting it after anytime I say the "Glory Be." For instance, when saying night prayers with my 3 year-old, I usually say the Our Father, Hail Mary, and Glory Be, and then usually have to stop myself from beginning the Fatima prayer.