if everything is fine (no bad chicks) it's balanced for 3 per week on average pay (so happiness = indifferent)lol 5 or 6. im guessing now that my staff is entitled pricks who need short work weeks?
anything else you have to increase happiness anyway you can. spa visits, investments, policies, ...
also "happy" pay isnt enough for 6 per week i'd say. maybe with everything else in place.
at least in newest version theres operation modes for studios that decrease hap penalties from chicks with bad traits. also pa policy that lowers it even more, so you can dedicate 1 studio to shoot with them only.