NZFF

I eventually found it by flyng along a latitude until I reached the longitude. In AFS4 Ctrl+F1 toggles an extra overlay showing those and other info but it is in very fine print and if you want to capture it you need to use Bandicam or something similar, because it does not show for the default screenshot key (S or Shift+S). You need to approach on 156º and if you want to do a t'n'g you will need a 633 Sqn Mosquito or maybe a Moehne Dam Lancaster. The threshhold is 150' lower than the other end. I cheated with the Wilga to find that out. I will try with the Baron but it will need to be a very brief t and an immediate g . No way can you drop down in a fixed wing to get out in the other direction.
Thanks to DFW for the route map.