8_24 = 1/10Tp + 0,5 = 6,1 + 0,5 = 6,6cm
2_25 = 1/3 Largeur du dos + 2 = 6,6cm
1/2 Tt + 2 = 29 + 2 = 31cm
1/2 Th + 2 = 31 + 3 = 34cm
34 - 31 = 3cm