You might find some posts on this in Tips & Tactics.

IMO the Planesman is the most important sailor on a sub (besides great engy/s), so I would class on time.  Also a boost would help.

The Sonarman could be classed later after the first promotion.

Don't forget, UK sailors get +2 rep/rest anyway.

Engie stat ONLY works on Engineers.

I've only got UK SS4, but from what I've seen/read, the SS5 is disliked mainly due to only having 4 forward tubes & no rear.  Mind you, it could fit 4 engys.

Let's talk about ss UK ss speed OH is ok about 37-40 up to your eng turning force is enough for ss fight but only ss5 that has only20turning force that make it crap but UK have ss5 have alot space for armor my ss5 OH37 0.6belt 2bulkhead so it can help me when i surface near bb and scout is usefull in HA or blind game atleast u are the last one u can see the enermy Trop dmg quite low but reload faster than ijn ss5 and the big gun can make big dmg about2000-3000 it alot when u hunting CV it a big fun Have u ever play uk ss4 and out of trop this one can load47trop but 1suggestion dont run to KM ss or in ss wolfpack cuz u dont have stern trop

Class the planesman ontime and sonar class late