Hey Venatore,
I just used the same method like you and came to the conclusion that "my" u-boot would be...
U-659
It seems that U-659 sunk after colliding with U-439...
"Sank at 0030hrs on 4 May, 1943 in the North Atlantic west of Cape Finisterre, in position 43.32N, 13.20W, after a collision with U-439. 44 dead and 3 survivors"
http://uboat.net/boats/u659.htm
How unlucky have you got to be to crash into another u-boot in the middle of the Atlantic? :rotfl: