If you have any concerns about the metal ball ends of your strings cutting into your tailpiece and slipping through, here is something to try. My strings are Innovation Golden Slaps and they end with a little metal bar instead of a ball. I was concerned that they might slip through if they twisted. So I cut some disks from a synthetic wine cork and used a leather punch to make clean holes in the centers. I would not do this with natural cork, but the synthetic stuff is durable. If this is not enough to give you peace of mind, you can add a nylon or zinc washer between the ball and the cork.