If the block coefficient (Cb) exceeds 0.68, the tabular freeboard specified in Sec. 42.20-15 as modified, if applicable, by Sec. Sec. 42.20-5 (b) and (d), and 42.20-20(a) must be multiplied by the factor (Cb + 0.68)/1.36. [CGD 79-153, 48 FR 38650, Aug. 25, 1983]