Make some awesome Ultralight gear. Mostly I like their sleeping bags and insulated clothing. For many years I have used the UL Super Spiral Down Hugger #3 now called Down Hugger 800 #3 & available at Larry Adler Australia for A$329). Mine was 624 grams and rated -1C. Montbell have even improved this bag by moving to 1 oz more (and) of 900 fill power down. This is the Down Hugger 900 #2 at 690 grams and -5C, which is just awesome! This ‘spiral stretch’ construction means that they are the roomiest sleeping bags you have ever used. You can even cross your legs and sit up in them.
In Australia you will almost never encounter conditions where you will need a warmer bag than this. If you do (and as I do) you carry a down jacket and vest, you can put the jacket on and pull the vest over your lower body. This will provide at least another 5C worth