However, Hsu Sensei corrected the way I hold the shinai with my right hand. I should hold it in such a way that makes the V-shape more apparent, facing myself. In other words my index finger is less perpendicular to the hand grip. This way, I naturally use more of my little finger for clutching the shinai.
I really want to get the speed up with my men cut. The slowness seems to have something to do with my foot work. Maybe it's because I don't push fast enough with my left foot, and my body center is not low enough. An indicator is the sound of fumigomi. The ideal should be a sharp "slapping" sound as almost all the japanese kendokas seem to have somehow.