To fit three plys of 1/16" thick veneer into a 7 7/8" inside diameter cylinder mold, precise measurements are crucial. Each ply will reduce the effective diameter as they are added, requiring careful calculations for length. The total length for the plys must account for the thickness, ensuring a tight fit without gaps. The user provided calculations for various diameters using Pi, indicating specific lengths needed for the plys. Accurate dimensions are essential for achieving a snug fit when the plys are compressed by air pressure.