By kind permission of Neal Stevens (owner of SubSim), the NYGM supermod is now available from this link:
http://www.subsim.com/mods1/nygm/
Alternatively, click on my signature, below.
This is after continued difficulties with the FileFront web-site.
There are several NYGM manuals, since each new release has its own additional features. They are all collected together in the documentation folders for:
1. the NYGM 2.5 stand-alone version (the largest manual);
2. the NYGM 3.2 additional overlay.
Stiebler.