I am going to put everything about delaying into here.
I will do what I can. Please contribute to make it the best.

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(1) What.
Each nation provide a different set of crew title combination. Some nation got a chief repairman, some a chief engineer; some got a sq leader fighter, some a sq leader bomber. We used to delay carrier pilot, however, ability calculation changed after some patches, making it obsolute. Now, people delay for a better repair ability or lighter crew, at the same time trying to make sure everything alse the same.

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(2) When and Fact.
Fact first:
I: 8 delayed engineers overheat longer than 5 normal engineers, however, move slower in WAW mode.
II: They only work as a whole, so, if your BB1-2 in clan war give you only 5 slot, sorry your crews are useless. However, the BB1-2 may run faster depend on the kind of ship.
III: Expert gain rate will be lower.
IV: It need more vet than normal, however vet conversaion rate is lower.
V: It assumed you boosted everything.
VI: If you delay engineer, you should not have repairman onboard.
VII: you can sell them alone hardly, no one will buy it.

When should I delay:
I: torpedoman for SS6, not the slim skeleton torp on DD.
II: always delay Operator to any level if you can.
   (let's say BB3 have a typical range of 34, your gunline at lvl is 30,let's say, you cannot see it.
   If you delay your BO, your gunline may be 29. So tell me, what's the difference?
    You shoot with feelings!)
III: USA, UK, IJN AA gunner do not reach reload cap on normal class.
    (Optional for KM AA gunner ifyou want accuracy on it.)
IV: HH gunner on Carrier.

Optional case when I consider delaying:
I: try to make light weighted crew so a list of big ship move 1knt faster
H39, Kasier, Project 24.
II: try to get 11.0 inch of armor and above on QV, with a reasonable OH duration.
III: try to create stupid combination to play.

When you should not delay class:
I: I find that my BB3 is easy to die
II: I find that my BB3 move slower when crew level up.
III: I know that SN & KM bad in repair ability, it seems not enough even with repairman.
IV: People said sonar and planesman will reach ability cap soon.

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(3) Cost and risk
Risk:
well if CCP collapse, you become one of the dude crying, or,
if new patch included ask you to have repairman independently

Cost:
expert pack after 300% event. With normal crew, I will grind the expert back from gameplay. However with delayed crew, vet & exp are your life.
Although it may not cost you more money, your time is a must.

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(4) How
I: Typical:
start with 4 elite rep 8 11/x/12, and 2 ghost sailor.
make them 2 armement, 1 sailor, 1 special force, 8 support.
Class them at least after 100 levels as gunner, BO, rookie, engineer.

II: cheap guy half delaying:
start with all non-elite sailors.
Get them 2 armement, 1 sailor, 1 rookie, 10 support.
Class them at 70-79 lvl as gunner(cheif/huge anything), BO, rookie.
keep 8 support as 2nd engineer, keep 2 supports for HH

No one delay engineer when they have repairman.

No one delay sonar & planesman
why?
firstly, I can't reach planesman cap(4.6M TA).
Second, it is easy for sonar to reach cap only under water.
If you put sonar on carrier(likely PCV or CV5/CV6), you need 3.6M TA and above.
If someone need proof, it will be a whole new topic.

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(5) Comparasion

Do mention again on top, it's only working on BB6 and BB5 at best.

Need a primary crew that can power level them, that can sacrifice support slots.

You have to level an equivalent of 2-3 bb6 times to level them. A bb6 grind fastest way is 1 weeks playing 10-15 hours/day. Equivalent to 2-4 months grind for someone that have a full time job.

Now 2-3 bb6 grinds, is about a year grind for someone with full time job.

Cost about 400-800 USD$ to get the acceptable amount of vets. Or 3-4 years of AAing and waiting for events to get an average of 250-260 vets.

Wasn't the cap for sonarman between 2-3 mil?

>Wasn't the cap for sonarman between 2-3 mil?

they said, under water 2.1M something, 3.7M something above water.
but their experiement was not on our server. 


TSR ＝ Vision X effective Sonar ratio
effective sonar ratio ＝ 0.268 × Log( True Ability / 2512 )


where effective sonar ratio has a lower limit of 60％, upper limit 85％
430k TA is same as a ghost sonar, カンストは約373万となります。 ?????

I remember when Adalbert said it's around 2-3, and he states it is possible to get a higher but even non conventional crew needs crapload of vets tough.

Last 2 years, it was still valid. Didn't check if it still does now.

Might consider 2-3 as the "possible reach" with the "best bang for the bucks" with delaying.

Adalbert's testing was done in the stone age tbh. The data on sonar and planesman is outdated, it's incomplete at best or incorrect at worst.

Remember back then having 150 veterans on sailors was considered a lot, thanks to all the conversion events that's far from the case now. Also he isn't assuming we'd all have lvl 100+ sailors for everything. What he considers to be unrealistic abilities are easily obtainable now .

we used to have ss2 only when the great Adalbert run the test.
and the cv's were not able to see ss along the days.
test used to be run under water.
The value is still correct, 2 TA to 3 TA somewhere capped. It's like log value round up.

I really have no intention to verify but I buy the point to get extra TSR for my CV.
and, we have waw mode now. 

I will try to remake the table into english version and host in somewhere else. 

ok, since the server is down today, I am going to update this post :D
(*1) the table is not necessary to be correct but it would be a good start to understand things.
(*2) by the time they do test, there are SS4 only.
(*3) from the table, we can see that SS1-3 get a better range when submerged.
(*4) we see that on SS4, it give you about 1 extra TSR for not delaying, when cruising on surface.
 
For 2150k true ability, it is achievable by delaying 2nd sonar class to 120.
(ie, leveling up support sailor from 12 to 120, POT+10 , 200vets)

For 3730k true ability, it is achievable by delaying 1st sonar class to 120.
(ie, leveling up 2nd sonar from 12 to 120, POT+16 , 200vets)

For WAW mode, I would like to have a normal sonar for all the suprise from future.

What will you choose? 

If one were to have a complete hero crew, would it be worth it to delay class the entire crew until Bb3 level or Chf Engy/1st Rep lvl?

Trying to built a 39knt Kaiser with AA (10 binds), 3 HE 2 AP and 0.2 belt. 
I just started the lvling, but it will take some time to finish, as richardphat stated.
I might post my project on navyfield.com after I finished the grindings, if the game still excists by then.