Which kind of train? 1x1? for Guards of Forwards?
Definitly that would mean that even for a 21 year old to pop in driving is at least 0.5 per train. Taking your trainee as an example and assuming he poped on the first train you gave:
Inicial = 7.9 (Respectable)
7.9 -> 8.4 -> 8.9 -> 9.4 -> 9.9 -> 10.4 (Prominent)
Of course this would work even if he had 7.5 being the minimum of every train ate least 0.5 (with 0.4 it doesn't work).
Keep on giving us informartion, this is really nice