At what age or height, did your child stop using a car seat?
My son is 4, and he is tall (110 cm). Our rear car seat does not have headrests, and if sat in his car seat, or simply on the booster, his head/neck is at the height that he would have limited support, and therefore more whiplash injury. We therefore think he is safer without the booster. But if we sit him without a car seat or booster he isn't comfortable. His legs are not really long enough to sit comfortably without a booster. (We do have a seatbelt adjuster thing, that's not the problem).
The Concord carseat with adjustable headrest looks good, but I don't want to spend more money on carseats if he doesn't use them for long.
Any advice welcome!