In my Hyundai, ds definitely needs a booster to be safe but in my adult sons Ford, which does not have headrests in the back, a booster puts ds too high up. Fortunately, the belt goes low on his hips without a booster. Ds2 rides in it maybe once a week, so I am OK with him not using a booster.
Do others go through phase as well, where their dc uses a booster only in certain cars? With ds1, I was way less informed... I just arbitrarily chucked the booster into the trunk on his 11th bday. He was the last of his friends to be in a booster and I thought I was mom of the year, Haha
I need the BTDTs for my exdh, who is going to hear from ds2 that he is starting to go without a booster and will want to stop using one altogether. The problem is that I know how to tell if it's safe and he doesn't, so I just keep drilling it into his head that ds can't ride without one.