Braided hat help

[B]help with sizing the braided hat pattern [/B]
So the hat is modeled on a child but if I am using Patons’ sws I have cast on 120 to fit my head-average adult, to do the ribbing. then what should I decrease it down to before starting the cabling? Or should I just frog the ribbed part and start over? I actually like the ribbing so I could keep it and fold it up over the cables a little bit?