My best was a 3.4km shot that sunk the Illustious off Norway. I was not in a great position as the TF can cruising past at 25kt so I ran a flank to get as close as I could and then let loose with a salvo of 4 eels from about 3.4km out. All running slow set 3 set for impact at a depth of 7m and the first for magnetic firing at around 11m depth.
The first eel struck just under the smokestack and she started to slow down. The other 3 then hit one just forward of the supersrtucture and the others midships. As the 3rd impact hit when started going down so I must have hit her fuel bunkers!
What was so satisfying was that the rest of the TF just kept on going so I didn't even hear a ping from the escorts!