i go with light BO and light sonarman. that means burn them ,i got vets i have from playing/lvling to ss1

( like ur m8 says why : it works just fine this way and is lighter )

trim the torpper a bit

( why: after a while it is just as fast with out some crew ,don't break his reload)

and u only want to have more than 100 vets on ur engy's and ur missing repair man

(why:faster and faster overheat and faster rep)

and a little bulge

and for ur ijn ss4 to got 39 knts u need u need very good and or high lvl engy's

ghost ur BO - his bonuses in a sub are meaningless when compared to the needs of ur engies and torpman. Watch the cap on ur bow torpman and pour the extra sailors on the engies. Can't really comment on the sonarman as i don't know how that sailors works.

For you: 3 eng ?? drop 2 and see if that helps.

In general:

subs are too light to carry much, you have to drop a sailor or two .

Heres one solution:

Drop the gunner first.

Drop a stern torper second

Drop the eng. third

I just play with one slot open.