Based on the information provided I would be looking at using a different projection which is not tied to the UTM Zones, like Geoscience Australia's Lamberts Conformal Conic Projection. This will have some distortion effects but they will be minimal. The distance units are then in metres. It should also get through the issue of the state crossing as all agencies are meant to be able to use this projection as GA is the primary mapping body in the country. Check with your requirements as this may be an option.

The projection is available for download if not provided from GA's website.

have fun, CDB

Based on the information provided I would be looking at using a different projection which is not tied to the UTM Zones, like GeoScience Australia's Lambert Conformal Conic Projection. This will have some distortion effects but they will be minimal. The distance unit is metres. It should also get through the issue of the state crossing as all agencies are meant to be able to use this projection as GA is the primary mapping body in the country. Check with your requirements as this may be an option.

The projection is available for download if not provided from this website.