In the following link, Rav Ovadia zatzal's opinion is quoted that Sepharadim should wear the tallit katan inside, following the Arizal. Cited by Rav Mansour is also the Mishna Berura's and others' opinions as well. Everyone should follow his own Rav.
BE"H soon, in memory of Rav Ovadia we will soon start to learn the halachot of tzitzit according to one of Maran's namesakes, the Ben Ish Chai zatzal. May Maran's neshama have an aliya and may he be an advocate for all of us.