you won't have much displacement to work with and you shouldn't be overheating. So a low level nationed elite engy would give you good normal speed. then you'll only need a bo (keep it light and low), and the neutral torper. You really only need one sailor to drop dc because you won't be using the midship dc's much. So you only need the one torp sailor. As an afterthought, you might consider a good ebve low level sonarman, the ff will spot subs but a good sonarman helps.
Ship Setup:
Rear DC only
Armor (none, you're using rear dc's so you won't need bulge, neut armor = useless anyway)
Crew Setup:
BO (something very light)
Gunners (none)
Torpedoman (neutral with good torpedoman stat, only need 1)
Sonarman (something light with good ability, not necessary to have but helps spot further)
Engineer (something light with good ability, also not necessary but helps)