The 0.75 supposedly relates to 75% of shots taken are duds. As you found, that does not exactly correlate to what you have in-game. Similarly, you found that the 0.2, relating to a 20% failure rate for a 1-in-5 chance of a dud also is a bit "off" the mark... Be aware that there are quite a few settings in there for the dud factor. If all you changed was the depth-keeping failure rate, but left the impact pistol portion alone, then perhaps you need to raise that chance a bit. Or maybe the magnetic pistol works too well? A combination of both? What I did in FotRSU testing was to work on one aspect at a time, and then use the external camera and the F6 Attack Map to "follow" the torpedoes to an anchored target. I would try with all parameters set to a 100% failure rate except the one aspect I was working on. Get that setting(s) written down, then move to the next. It takes a while, and setting up for an "angled" shot can be time consuming, but the Mission Editor can help with that somewhat...
