NZ pine, is an ironic title, as its actually native to USA, if its Monterey Pine/Radiata Pine.
Grown in massive softwood plantations in Australia and NZ. Quite a useful wood, pretty tough, but looked on as a poor man's wood due to the huge amounts of low quality factory furniture made from it.
As a kid, my Dad a forester in Australia who used to manage the Radiata pine plantations made my brothers and I some bows from green, osage saplings(he knew osage would make a better bow than pine). My friend wanted a bow because I had one, and his Dad made some bows from pine saplings. They worked quite well for a while until they dried out and broke.
The osage bows only got better as they dried out.
Anyways you're getting some success with it, so well done.
Have you tried heat treating it?