Hi, I was hoping someone could help me with removing/opening my Dunlop M-Fil 400 butt cap. I see there's a notch in the butt cap and I know it's supposed to open up somehow so you can put weight inside the handle. Does anyone know how to do this? Does it require a special tool? I bought the racquet online and if it does require a tool I don't have it, is there some way around that? Thanks.