With GWX installed the DD's will (not might) spot you from VERY far off. So I personaly hit "Dive to PD" at any spot report from the watch. While the boat is submerging, take a peek through the periscope and try to identify the vessel. If it's a DD or Escort, contiune to PD and start plotting thier screen patterns. If it's a merchant, I surface and try to get better postion before going back to PD.
Rig for silent running and point your bow into the on coming ships. Make sure you keep your speed around 2 to 3 kts or your conning tower will break the surface. Get under the DD screen, turn 90 degrees towards the track, fire, and prepare to get pounded.
