I've just bought a britax evolva 2-3 car seat for my dd who is 33 months old. She is tall for her age and has outgrown her britax 5 point harness chair that's ment to go up to 4 years.She is 18kg. I've heared people say that this is too young not to be in a 5 point harness. Is this true and if so does anyone know of a make of seat that has a 5 point harness for a child over 18kg. She is very mature for her age and would not pull at the belt. What do you think?