Haven't made that experience that torpers don't get any XP.
General problem is, that they get less XP than gunners - some say torp damage generates only shared XP. However, leveling Kita and Sub is somewhat slow leveling.

About weight problems: Yes they can appear on subs.
You have the option to reduce crew (take of red rookies) of BO, sonarman and rear torper. This  will them make losing abilities but still keep them working. But you won't have to take crew off unless your crew is maybe 20+ levels above ship level.

Some other ideas:
- If your BO has good potential value (14 , 15 or elite) better use him for Kita => BB line.
- Your sub BO's potential is unimportant unless you want to drive premium BBs with it (it effects guideline lenghts which you don't need on sub). Better get a BO with good restore and repair values.
- If you're going down BB line your BO will become too heavy for Kita some day, slowing it down significantly. If Kita gameplay is soemthing you like you should consider making a third, light weight BO.

Thanks for your help Harry,

I guess my real objective is to play on an SS, but I want an advantage over subs that might be on the same SS as I am, and be a pain in the neck to the SS class higher than my own. Which is why this idea occurred to me. I used to play on a Kita as my main ship but when the SS came out for the first time, I hopped on the vickers and transferred my torpers over from the Kita. It gave me a clear advantage over some of the starting SS because I could reload my torps faster than they could.

i'm thinking about just going straight to SS, but i want to confirm whether or not my original idea should be the route I take or not.

The challenge with starting the SS line immediatly is the low exp, thus the long grind between SS1 and SS2. I became frusterated with the SS1 as it has low speed ontop of short air supply. Thus I reverted to earlier ships anyways with my SS line. 

As for your advantage over other SS with your improved sailors. I find that driving and the duds make a bigger difference for success with SS, rather than slight reload advantage. 

IMO its better for you to go Kuma line before going SS line.  As mentioned by the guys at top SS1 grind is very very hard using at level crews... If you have already higher level torpers and a decent engineer (70ish) then yes SS1 is feasible but if not go for Kuma line first and level those SS supports and torpers before going SS line.  BTW Kuma line is a good ASW ship at level.

When I was in IJN SS1 its really sucks, but the technique on SS1 is.. you don't have to rush to the BB's the only way to get damage on SS1 is to let them come to you..

i

 regarding ss

f u want the advantage youll want the best torper, sonar and planesman, especially front torper and sonar.  if youve only got average sailors.  id start again if your under lvl 45.

elite and boost the lot with 100 vets on each minimum.

for ss4 youll need 1 torper, 1 sonar, bo, 3 engies.  u need 5 engies for ss5 but its crap so dont worry about that.  ijn ss4 at 100+bo lvl is the best.

theyre are ability caps but if u want the advantage that what its going to take.  especially because ijn ss is hard to ss vs ss in thats why u need a good sonar.

im sure ppl will disagree but thats my 2 cents