This is about the same problem but using the Maneuve-Board in a classical way with the convoy always in the center.
x0: initial position of u-boat before attack
x1: desired attack position on the 3. row of the convoy
x2: desired position after diving under the convoy
x3: desired escape route with 2kts speed.

To find solutions for heading & speed use
Maneuvering Board Pub 217, 1941
x0,..,x1: 183°@1.6kts
x1,..,x2: 150°@3.0kts
x2,..,x3: 197°@2.0kts