When it comes to planning for the voyage from New Caledonia to Australia, we look to mate, Rod Waterhouse.
Rod has salt water in his veins. Rod has crossed oceans in hobie cats, won international sailing races, held world titles & like many of us he has also spent many years cruising  the oceans of the world with his family.
As well as being a mate, Rod & his partner David also support the rally as rally partners. Check out their profiles DBY Boat Sales & Just Multihulls on the services page for more info on what services they offer participants of the rally.
This is what Rod has to say about the passage "Down Under"; 
Hi Everyone ,
I am really excited to be part of  the 2016 Down Under Rally & I look forward to meeting you all as I visit the the islands myself later in the season.
In regard to the passage to Australia I like to emphasise that I am definitely no expert in this field. My information is compiled from the same weather and related sites you look at. I combine this info with my personal experience and knowledge that I have banked the hard way.
The info I have provided below IS MY OPINION ONLY and BASED ON MY PERSONAL EXPERIENCE. It is not intended to be "HOW TO". As with all passages the captain of the vessel is solely responsible for the safe arrival of the vessel & crew at the next port.
I have been traversing the New Cal - Australia crossing both ways for many years myself and have also had the joy of assisting cruisers by providing them with suggestions regarding routing. Over time you get the feel for the run.
I am available to all rally participants prior to your departure and during passage for advice, just Sat phone or email whatever suits best.
The run from Noumea to Australia is typically 6-8 days dependant upon your chosen port of arrival and vessel.
The good thing about sailing to Australia is its a massive target. Distinctly different from trying to arrive at a reef strewn Pacific Atoll. The best parts is that the east coast of Australia offers several choices for your port of entry.  
These choices mean, that should the weather not be as expected, you have plenty of options. You can make as much as a 90 degree turn to afford a more comfortable voyage or simply choose an alternate port of entry.
In saying that, I rarely have not made my original destination. Last season, having routed around 20 boats, the majority made their port of original intention without diversion. 
The passage to Australia is usually very predictable. It does get easier to predict and weather windows longer as we advance into Southern Hemisphere summer.
Typically I find favourable weather windows sailing east to west of around 5 days in winter May-August stretching to 6-8 days in Sept-Nov.
Remember that Dec-April this region is prone to Cyclones so no go for me anyhow.
Looking Forward to meeting you all soon