i use 100.5 meter balls for measure. i stack them up until they reach the height of the tower. if the top of the tower dosent match up with the top of the ball, i cut it and place it as 0.5, 0.6, or 0.4. for instance, my tower was 71.5 ballic units tall. so i multiply it by 100.5 and get my answer. i then divide it by 3 and get my answer.