Just make sure you don't accidentally fire staff, if some groups are over 100%.
it seems firing a few people doens do any damage. i had all at 100 points of happiness (except me and high level management); i had some people 2 -4 people more than needed. firing them made happiness to 98, which is not bad. company image of 70 points was not affectd.
HOWEVER, I later reduced peoples' salary by 20% (some people in my contry due to crisis was cut 25-30%, many firings "by your own wish", high unemployment, bancrupcies, etc) - and company image fell from 78 to 40 immediately. load factor dindt seem to suffer too much.