Hi Mike
I'm not quite sure why you don't just produce a metric set of drawings and calc everything in metric from the get-go. However, assuming that you've already considered this (or that I'm just missing something), you might consider looking a little further north to your metric Canada colleagues: there are some good references available from the Canadian Wood Council, online at
www.cwc.ca In particular, the Wood Reference Handbook is a good read. (We're in an active seismic area here in BC too)
BUT, don't forget to untangle your wood species from the calculation process: make sure you are using the correct timber properties, because NZ doesn't share a lot of timber species with Canada.
By the way, you'll be cheered to know that there is a small but significant Kiwi tradition of timber framing, and there are a couple of active framers down there too.
Best of luck with your project!
Gord