Fwfian,
I haven't calculated how many hours of sleep that my baby son had when he was 6 months old. I think the baby should approximately take 2 to 3 day naps. Each nap lasts for 1.5 to 2 hours. It's good for the baby to take nap after each meal. It is because sleeping is important for the baby to develop his brain. Of course, when your baby gets older, he doesn't need many hours of sleep. My baby takes 2 naps a day now. One in the morning, one in the afternoon. However, when there is activity attracts him, he will skip the afternoon nap which I don't want him to skip.
By the way, the baby will not be too chubby if he only eats but not sleep.