These are all personal preference and you may not notice the failure rate changes over 1-2 torpedoes but you will on your entire payload over your whole patrol. In my May-June patrol, I fired all 14 torpedoes out of my VIIB during the whole patrol and scored 6 hits, 7 were failures, 1 was a human error - miss due to my miscalculation (this is during the time of the highest failure rates in hsie, sept 39-may 40 and it works as intended). Sh3 simulates failures in three ways either premature explosion before hitting target, running too deep or bouncing off hull - hard to do unless you have bad angle with impact shot or you use a magnetic shot that hits the side of hull instead of going near bottom of hull. I have to resort a lot to using my deck gun early war to finish off a merchant because of damage or take one out due to failures as was historical, they achieved better success with the deck gun then their lousy eels in first year. If I can tell she's unarmed and if there's no other contacts around I may not even waste a torpedo and just use deck gun- provided its not more then 7m/s seas.
