This technique is now battle tested and works way better than I could have hoped for.
The situation:
I was playing the photo recon single mission. In this mission, I did not have radar. I had already completed the photo recon part of the mission and there where 2 destroyers ahead of me about 5,000 yards distant, and a destroyer behind me about 4,000 yards distant, all of which where looking for me and royally ****** off. When I came up to periscope depth, I saw a Nippon maru in the distance, which was my last objective.
I quickly determined that a collision course intercept was out of the question, the angles where just wrong and I had to stay at silent running if I wanted to get my fish off. This meant that I had to head right towards the firing position and risk a long range salvo. Since I did not have radar, the best tool in my arsenal was measuring his length as I've been discussing in this thread.
As you can see, looking at the plot, my first two readings (marks 23 and 24) where off. I attribute this to his AOB just being too sharp. It should be further apparent that measurements from mark 26 onwards where right on the money, with an average error of maybe 25-50 yards. Considering that every one of these marks where visually measured at a range in excess of 5,000 yards, I consider that margin of error to be outstanding. Examining mark 26 in further detail, I can tell you that his AOB at that mark was 38 degrees and his distance was 11,200 yards.
The end result of this track was 4 mark 14's fired from the bow on fast setting at a range of about 4,600 yards. If you know your mark 14s, you know that this is out of range, except that this is his range *when you fire*. He actually closed the last hundred yards in time for two of my torpedoes to hit him, slowing him to a crawl so I could finish him off later at my leisure.