I think you've misunderstood what the purpose of this approach is. It's not intended for long range shots, just for gathering speed data. My point is that unless you have visual AOB (and greyrider, as i can, can determine AOB visually, reliably and accurately) then you do not actually get a speed estimate with this method, unless you guess, and that guess turns out to be right.
There are ways of doing it. Simply put if you have made an ISWAS or Submarine Attack Course Finder (and i'm surprised you haven't, RR), you can get a range datum after you have established a collision course, by changing your speed for a short period.
You can obtain a second datum by doing it again later once you are nearer the target, or even using the point at which the target arrives in front of you as the second datum
here's the link to the tutorial i wrote nearly two years ago, although i have refined the method somewhat since then
http://www.subsim.com/radioroom/show...highlight=SACF
but nonetheless given a choice a couple of periscope observations makes a lot of difference, and more fun is to use the Submarine attack course finder the way it is intended.
As for using non-historical options - play the game how you want. obviously historical skippers were constantly trying to optimse their performance with better techniques and newer technology, and ultimately as time progresses they succeed, but in practice they had limitations that we don't necessarily have.
if you want you can use your boat's hydrophones like a modern sub will, since the bearing report by the sonarman is much more reliable than it was in ww2. You try getting a long range bearing by listening to the hydrophone yourself and detecting when it's changed by exactly 1 degree. It's not at all easy!