I take 50mg to help me stay asleep and it is severely sedating. My Mother is on 300mg and has no trouble. I have a friend, 6'3" 240 lbs who was on 50 mg and it knocked him right out every day when he wasn't supposed to be sleeping. My girlfriend's friend is on 700mg and he functions just fine.
By the way none of us had any weight change with Seroquel. Zyprexa is notorious for causing weight gain.