Hi
I have climbed one of these beautiful trees. It was in a park though not in the forest (unfortunatly). Around 140ft it is semi mature. They have thin bark so please use a friction saver for drt. A big one cause the first limbs are hefty. The biggest challenge is getting your line up cause the first limbs are high. I would say big shot required. Limbs get closer the higher you go and it gets easier.
If you're going to New Zealand be careful where you climb as these trees have spiritual value to the Mauri's. Show respect.
Dont know where to find really big ones in Aus I think the NZ ones are bigger.
What part of Aus would you visit?
Cheers