Hi Galahad78!
You are right, electric are the coastal USN submarines with Mk.X, obviously they have not the dude problems that that their bigger sisters with Mk.XIV.
Selecting a correct patrol war area is valuable, forget warships, patrol into japanese waters nearby the main ports: Kushiro, Ominato, Hakodate, Tokyo, Osaka, Hiroshima, Sasebo, Keijo, Port Arthur, Shimonoseki, Shangai, Toyohara and Shikuka, avoiding mine ports, patrol 40-120 miles..and you will get victims if your enemy have not a good convoy-asw system.
In the screenshots are the USN submarine in the war patrol areas at Honshu-Shikoku-Kyushu areas:
16 submarines are patrolling in the Yellow Sea-Honshu-Shikoku-Kyushu areas.
5 submarines are patrolling in Hokkaido waters (USS Skipjack, USS Spearfish, USS Saury, USS Plunger and USS Sargo).
Another 4 electric boats are in transit to their war patrol areas in the Yellow Sea (S-36, S-37, S-38 and S-41).
08 oceanic submarines are in patrol in the Carolines-Palaos area to attack enemy shippings to South Seas (several messages intercepted by HYPO reporting 4th Division targeting Port Moresby---now, I know this was a deception message, the 4th Division was unloaded at Koepang yesterday!)
