shear capacity of gypsum board

Why doesn't that table in the IBC work for you?

The Australian Timber Framing Code AS1684 gives the following bracing capacities for nominally fixed plasterboard walls:

One side sheeted - 0.45 kN/m (30 lb/ft)
Two sides sheeted - 0.75 kN/m (50 lb/ft)

Well, I am actually checking the design of an existing facility, and the spacing of the studs are different as well as the nailing pattern than what the table has. There is also sheathing on both sides. Intuitively I was thinking you could just double the capacity then, and I was mutiplying the table capacities by the ratio of the stud spacing. But, I'm not sure if this is really correct, so I wanted a reference to see if these assumptions were correct.