Thanks a lot Obst.

Because of you my ife is going from better to more better

You have to differ some terms strictly.

Ability = The rought values of ability Experts+Vets provide
Skill = The stat that is affected by the Growth

However, I think everything of importance is in my Guide on Recruits, Experts and Vets:

http://www.hosting.nsagames.com/obst/NF_Guides/guides.html

:EDIT: I have updated the Recruits/Experts/Vets Guide to cover your question better :D