I would let him guide you. He might need a variation of 3, 3.5, 4 throughout the day. If he has an A time of 2 hrs, then sleeps 2 hrs, feed him when he wakes. Then he might have an A time of 1.5 hrs, sleep 2 hrs, so just feed him when he wakes. I would be cautious, though, of naps going past 2-2.5 hrs as you don't want to completely through the day off.