I had seen a lot of top drive installs using thicker carbon rods but all I had was music wire so I wanted to be sure my holes where tight going through the foam and also the placement had to be accurate so I made a guide and use a cigarette lighter to heat the burn wire. I was also very careful about not enlarging the exit hole through the kevlar. The rod has to flex a very small amount near the horn so the foam has to be slotted at that point. I did that with my dremal wheel. I managed to get a dymond d4.7 under the skin surface on the bottom side. Very tight fit indeed.