I had problems with hitting targets too, until I found this thread. However, now that I'm on the mission where I have to sink 5 AMC ships and I have 4 Type II torpedo's loaded, and it doesn't matter what I do they keep missing using this method...
Does this method only work for the Type I torpedo's?
Edit: Nevermind, read on the first page about torpedo speed affected by torpedo officer upgrade. Will try the mod given