So there are some notecharts that contain double slide arrows in either direction. I don't have any issues with the ones that go in different directions, but I don't know about the ones where both of them go the same direction. I use my DS3 controller with Motionjoy, and I have remapped the slide arrows so that L=L1 and R=R1, but there isn't a way (that I know of) to remap so that double-one direction arrows can be hit. Does anyone know of a solution to this?

You can use Triangle button as Left and Circle button as Right Slide.