LaLa, I talked to the police officers in IC just a couple of weeks ago when I was trying to figure out what to do with the booster we bought for Christian less than a year ago. He had grown too tall and his shoulders were above the straps (it only had two heights for the strap adjustment) so I had him in it using the car seatbelt -- he weighs 35 pounds Cosco (the carseat maker) told me that once he was 30 pounds I could use the car seatbelt. I wasn't quite comfortable with how the seat routed the lap portion of the belt. It seemed to go way to high on his stomach. The whole point of the booster is to raise them up and make the lap belt go across their thighs, and not their stomach which is dangerous.
I just happened to run into the three officers who are certified car seat techs when I got to the bfing meeting one friday morning a few weeks ago. Before I got C out of the car I had them come and look at how he was sitting in the seat. They told me that until they are *40 pounds* they need to be in the five point harness no matter what the carseat manufacturer says. They also told me that the way the belt path was designed on that car seat was terrible and I should stop using it altogether since he was too tall for it (he is only in the 45% for height as of his three year check last year, so he is by no means tall) but he is only 35 pounds so can't use it with the car seat belts.
I just thought you could use the info.
BTW, anyone looking to buy a five point/booster combo -- DO NOT buy the Cosco brand. They are designed very poorly. I'm now trying to figure out what to do with the booster we used for less than a year, that we figured C would use until he was big/old enough to sit in the car with the belts.