Millefleurs,

This site "www.cumberlandgroup.com.au" contains a paper titled Sustainable development, Subdivisions, Surveyors and Sun Angles.

This paper traces the Observations needed to work out some principles for passive solar design & your eave length.

The EBS Bulletin "Sunshine & Shade in Australasia" will help you out with sun angles in your area. Use the chart for Melbourne as this will be close enough. Read also Bulletin 6 "Designing Houses for the Australian Climate".

In Northern NSW we've used about 57° as the sun penetration angle for the northern eave. Here this gets sun penetration starting and ending on the equinox. ie March 21, September 21. and this works pretty well.