The correct positioning for your child's chest clip: in line with the underarms (see above)
After I watched this, I was convicted of considering a cheaper, belt positioning booster for my daughter, even though I was going to buy a high backed one. Yes, some seats may cost less money, but at what real expense? Time and time again I end up going for the Britax line of car seats, which is what we just ended up ordering. We chose the Britax Frontier 85, which holds up to 85 lbs in a 5 point harness, and then something like 120 lbs. as a belt positioning booster. The price was not too shabby considering Britax is top of the line in safety, and we'll get years of use out of it. I can't wait to take my little girl for a ride in it! She picked the red one :) There are probably less expensive seats around, but none with such high weight capabilities. Do a little research of your own if you care to find out more. And remember to always keep that chest clip in line with your children's underarms, or they could actually jerk forward right through that open space in the event of a crash. From one mom to another: think safety first! Let's let Belle's life truly be a gift to each of us.
P.S. Don't even think about using a mere lap belt alone on your child..ever! Even adults can be killed by these. After numerous reports concerning their safety, these are being phased out.
Update: I just had to post these adorable pictures of Lucy with her new car seat. Her brother had just so happened to help dress her that morning, and she matched it so nicely! Also, she was thrilled with the shape of the box too :)