Here's the story of the Texaco SS Ohio:
http://www.usmm.org/malta.html
I've found the GW damage model to be very convincing. I attacked a convoy and made a point of targeting a large tanker. I got 2 eels into her, but was forced down and away by a DD and a Corvette working together (very realistic cooperation). I took about 20% hull damage from their pounding. I got a way and did an end run back into position, and found the tanker head down and listing to starboard very realistically but still making 11 knots and keeping up. I could not get into shooting position on her in the middle of the convoy, so I picked off 2 medium cargos in an outside lane. Both took 2 eels. The first slowed steadily after being hit and finally rolled and sank after about 45-minutes real time. The second cargo exploded in flames after the 1st eel, and the 2nd broke her back, and she went straight down in seconds.
I got another pasting from a couple of Corvettes and finally got away with 27% total hull damage. I did not risk another convoy attack that trip.