This has been answered multiple times (for special sailors at least), but I guess it would do for a nice easily searched thread in this forum.
Special sailors have a unique attribute that is applied each time they're classed. Two things will happen:
1) They will have their stats, including crew size, adjusted to what it would be if they were leveled up from the beginning and classed on time.
2) 30% of their crew total (after #1 is applied) will be set to vets. 30% to experts. And 40% will remain rookies.
Important things to consider:
1) #2 above overrides anything done to them before they were classed. If you add experts or roll vets, these will be lost. Conversely, loss of vets and experts during battle will also be erased.
2) Their special attributes factor in their current level at the time of classing. So you can level them up and get more vets and experts than you'd have if you classed them at level 90.
3) The attibutes are applied every time they are classed, so this means that you can class them to just below the final option (ie: 2nd/1st engineer instead of 1st/chief), use them as you level them, and then class them at 120 for massive vet counts.
