My DC are 136cm at 8 and 114cm at 5.
Both sit in this seat. Isofix still - firmly attached to the frame of the car.
www.capitalseating.co.uk/productdetail.asp?pid=969&type=s&appgrpid=&appid=&rid=67
Not only are they safe, protected as much as I possibly can bar leaving them at home every day, they are comfortable.
They fit in their seats. They can rest their heads, their legs aren't sticking over the edge of the seat like sticks becAuse their knee joints don't reach the edge of the seat.
I am a Lone Ranger that my 8 year old is in a seat, let alone a booster. They will be staying in these till they grow out which I think is about 148cm.
I realise they are expensive. My children were given them by their grandparent when they were 3 for Christmas.
Neither of them remember that fact.
I can see that an overweight child would not fit in my DC's type of seat. They are snug but they are supposed to be.