being the one who put this post up, I want to thank you all for contributing - maybe slightly less if you answer was more relevant to another topic...
I have not sailed in NZ before; mostly North Sea and Atlantic. And mostly 1/2-tonne, 1-tonne or big sturdy 50ft cruisers. In all you have reinforced my opinion about sailing that stretch of water in a small boat:
It looks to be about 350Nm from Napier to Wellington by sea, so that is quite a stretch for a 1/4 tonner;
Essentially there is no place to run or hide if the weather goes bad on that stretch;
I have just bought that bo