sorry don't have experience on this one, but i think you need to late class your gunners (staying it to arm sailor until highlevels) and you'll also need lots of vets and expert like 150 or more vets when you class him

Well, you would do that in order to have your whole crew reach the rep cap or save weight. You would leave the elite repair at UK sailor (not classed to any specific function like armament) until at least lvl 100.

So for having decent acc & rel while late-classing, you'll need to put on more than 200 vets. Oh, and it's advisable to put on vets as early as possible, as vet conversion success seems to be also dependent on sailor level.