I think it depends on what kind of sliders you plan to use, round tube or boxed. I used boxed and mounted em' flat, I think it works better as a step & a slider that way. When I hit em', they hit the bottom outside edge and have less contact with the rock. When a friend and I did his, he mounted his at an angle (also boxed) he has more contact with rocks and it dosen't work as well as a step. I think boxed sliders look far better flat too.
