Well, I'm behind you, having started my U-Boat career before TMO came out. I haven't gone back to port yet so can't install TMO. I don't know if it would be a good idea to install TMO while I'm running a U-Boat campaign anyway, and I hate the idea of installing and uninstalling mods depending on what kind of career I'm running at the time. What if I want to alternate days?
I can see a dual SH4UBM installation coming on: one for U-Boat, one for Fleet Boat. I'm still at sea in Kraken in my last patch 1.4 cruise. I won't be phasing out 1.4 until I return to base on that one. Then I guess it's surgery time.
But to answer your question, if it's 1944 or 1945 the Japanese DD fleet should be cut down to size by now and you should be seeing a motely collection of escorts, featuring the hated subchaser.