You don't need permission to wrench on your own game. Only if you intend to share it. As for where to look, in the Data / Submarine / NSS_Narwhal folder, you'll find the dat and other files that S3D can edit. You'll might want to noodle with the sim file, although a lot of the settings in there are not "real", and usually do not have any correlation with real figures, such as "11,500nm at 10 knots", would not necessarily mean that you would get an 11,500 nm range at 10 knots. You would look down in the "unit_submarine", under the "Ranges" section... but those figures also work in conjunction with other sections of the file, influencing battery recharge and other things, as well as working with some of the figures in the NSS_Narwhal.cfg file in the same folder. If ETR3(SS) comes along, he is a wiz at setting things, or maybe just has more patience with it than I do...
Anyway, you should "find" the best speed to drive the boat at for the best fuel efficiency first, before you do any editing, or if editing is even needed. If you are using TMO or some other mods, when on the NavMap (navigating) station, there should be a button on the menu that when clicked will calculate "Maximum Range at Current Speed", or how far you can travel at how fast you're going now. The thing to do is to set your speed, wait a few minutes, and click the button. Notate your setting and result. Increase of decrease your speed, wait a few minutes, and click the button again. Notate your results, and just do a few times from six to ten knots, and see where the most efficient speed is for the current settings. I'm not sure if Stock has that enabled...
