My son is 4.5, and weighs 40 pounds. He rides daily in a radian (FF), which has an upper weight limit of 65 pounds, so he'll be in that for a while I hope.
We are looking for a lighter, inexpensive carseat to use on a family trip that will be easier to lug around the airport. I looked into the cosco scenera, which was reccomeneded on a previous thread, but then I realized it's max FF weight is just 40 pounds, so it won't work. It seems like the other in expensive options are high back/low back boosters. These seem to use the belt that is in the vehicle-- they don't have straps in the booster seat.
I always assumed these were for older children-- are they safe for a 4yo? Does high or low back mattern? If so, it seems like a great travel option for us.