AS1170.2 is 96 pages, but it is broken into 3 sections. The
coefficients you quoted are from clause 3.4.12 (Section 3 - Detailed
Procedure - Static). Most engineers in Australia design using the
requirements of this section, which is only 18 of the 96 pages.
Having lived in Darwin,Northern Territory (Region C, Terrain
catergory 2.5 on figure 3.2.2 AS1170.2) for 25 years I have many
memories (not so fond) of going through cyclones on a regular
basis. Having experienced Cyclone Tracey in 1974 which
demolished at leasted 80% of all residential structures, I do not find
anything 'overkill' with the provisions of the code for ordinary
Anyway, enough of my rambling, Keith, there are some good
references on pages 90-96 of AS1170.2 that may help you.