Section 11(3)(c) in The Merchant Shipping (Equivalent Arrangements For Carriage Of Grain) Order, 1977
(c)For the purpose of demonstrating compliance with the stability criteria in paragraph 4(b) (see Figure 1), the ships stability calculations shall be normally passed upon the assumption that the centre of gravity of cargo in a "filled compartment" is at the volumetric centre of the whole cargo space. In those cases where the Central Government authorises account to be taken of the effect of assumed underdeck voids on the vertical position of the centre of gravity of the cargo in "filled compartments" it will be necessary to compensate for the adverse effect of the vertical shift of grain surface by increasing the assumed heeling moment due to the transverse shift of grain as follows :