Yeah guidelines will be too long... Of course why not boost him for some more ability? That can save some vets. If you care about guide lines being too long, you can start with a 14pot/12rep or 13pot/12rep sailor as a B.O.

In a classed-on-time sailor, boosting before or after classing makes no difference. But, yes there is a difference for delay classed sailors. Because, "boost works backwards".

 
Of course, boosting a national sailor (without a class) also helps with Repair ability and that mght be a plausible outcome. But there is the possibility of getting rid of the penalty of delay classing. Yes there is, AFAIK, and I confirmed this with moderators, (actually a moderator), "if you boost after delay classing, boost fixes the penalty of delay classing".  Interesting isn't it? Of course this can be a wrong information. But even if this was wrong, then that wouldn't hurt the repair ability outcome, you can reach repair cap without repairman.

lol

Yeah that doesn't sound good, I agree. But asking someone, who should have a fair knowledge about this game is not a bad idea IMHO. Anyway, you can reach repair cap without a repairman. Do you have objections to that?

No objections with that. We only want you to get it right before you recommend this to other people.

For the BO, I'd actually recommend an elite repair that you only make a KM sailor and class BO much later (probably at BB4 stage - I haven't looked into this in-depth), so that you can just put him on support or t-slots to make levelling him easier.

You shouldn't be recommending getting 11/11 gunners with 12 repair - where do you find them??? If you suggest putting 200 vets on them, 10/10 gunners with 12 repair do the job perfectly, and are already easier to find. I would even consider elite repairs for that purpose.

My own KM crew will hit the repair cap at 120, but with "only" 109-259 vets on sailors.

What I like about your idea of a setup is the engineers that are classed earlier than 120 (in your case, classed on time). But with your setup you are looking at financial overkill.

Actually, according to NFcalc, there is no difference at all in repair ability between a BO classed on time and a BO late-classed at 120.

Other than that, I agree with danita's observations, especially on the usefulness of a setup and trying to be efficient in vet numbers.

In practice there is.
Nfcalc gives you an end repair ability rating with a fully crewed BO.
You and I cut crew from the BO to keep the guidelines at max range.

Classing to BO never changes the repair ability growth. However the Potential growth will increase by 2 by classing it.
An elite repairer as nation sailor has 9 growth for potential and 13 for repair, an elite repairer as a BO has 11 growth for potential and 13 for repair.
So if you compare an ontime classed BO with a BO that is classed at say lvl 92, the on time classed BO has 160 total ability score ( to be multiplied by vets+ experts, corrected for crew percentage etc) more than the late classed BO, while their repair ability total remains the same.

A BB6 BO needs about 1.4-1.5 M TA potential to get the guidelines to the length of the max range of the guns.
Because the difference in growth speeds for Pot and rep are smaller for the ontime classed BO , it ends up with a slightly lower repair TA.

I put those numbers into Sk_bismarck's NFbuilder and made some fictional BO's, 1 classed on time the other at 92. At 120 with rookies removed to give the same potential TA:
Elite rep classed on time as BO ended up with 1.47 M TA potential and 1.74 M TA repair.
Delayed classed elite rep BO  ended up with 1.47 M TA potential and 2.01 M TA repair.

It's not a shocking difference, but every little bit helps.
Delaying the classing to 120 gives you  more repair obviously.

I can suggest you a KM B.O, based on elite repairman.

1. Class KM sailor at lvl 12, then boost, so he gets 11 pot, 16 rep, 11 res,

2. Class B.O at lvl 103 (now he gets 13 pot, 16 rep, 11 res growth)

(103 is H44 LvL)

At LvL120, He will have a crew size of: 684 (vet cap at 273,6)
His potential will be:1380 and his rep will be:1920

With 129 Vets and 550 experts: he will have 1'471'080 Pot with 2'046'720 Rep

With 180 Vets and 500 experts: he will have 1'839'500 Pot with 2'342'400 Rep

With 250 Vets and 430 experts: he will have 2'051'750 Pot with 2'745'600 Rep

 

Another possible scenario:

1. Class KM sailor at lvl 12, then boost, so he gets 11 pot, 16 rep, 11 res,

2. Class B.O at lvl 89 (now he gets 13 pot, 16 rep, 11 res growth)

(89 is H39 LvL)

At LvL120, He will have a crew size of: 712
His potential will be:1415 and his rep will be:1920 (vet cap at 284,8)

With 129 Vets and 550 experts: he will have 1'508'390 Pot with 2'046'720 Rep

With 200 Vets and 500 experts: he will have 1'839'500 Pot with 2'496'000 Rep

With 250 Vets and 450 experts: he will have 2'051'750 Pot with 2'784'000 Repp

 

Another possible scenario:

1. Class KM sailor at lvl 12, then boost, so he gets 11 pot, 16 rep, 11 res,

2. Class B.O at lvl 55 1. (now he gets 13 pot, 16 rep, 11 res growth)

(55 is  Moltke lvl, P Pro 1 at lvl 54 does as good AAing as Moltke)

At BB4 level, he will have enough abilty to see where shells land, and provide enough guideline lenght.

At LvL120, He will have a crew size of: 780
His potential will be:1500 and his rep will be:1920

With 109 Vets and 550 experts: he will have 1'479'000 Pot with 1'893'120 Rep

With 129 Vets and 650 experts: he will have 1'749'000 Pot with 2'238'720 Rep