Basically Wrinklednugg is right.
what do you want? I now play with it a fair amount, but not any real changes. 5 engies, plus a seaman in gun slot, sonar, plane, torpedo, and BO. Ship is still fricking slow if not in oh and ship turns slow. It is hard to play though if you get the BBs in front of you it hits hard. With this set up I easily have SD 900 and OH for probably 2 minutes. The best thing about the sub is it stays underwater a long time, so its a pain for an enemy without sonar.
Had to start using it because my sailors are just getting too high for the HEI to hold. HEI doesn't hold as many salvos as SS5, but is still faster and more maneuverable. I still like it better. Generally I still get more exp with HEI even though I take a large hit on ship level, because I have the speed to hit more targets.
Have tried many set ups with TBs. It takes too long to arm them up and get them flying to be worth much.
Capura has the best running SS5 I have seen, but he has level 120 engies. I don't know how many, he also runs at least 1 TB so that would say no more than 4. This is the only IJN SS5 which I have seen which moves significantly better than the SS4. His set up is a beauty.