No idea Mel, but you have 4kgs before you need to worry about it, then he can use the real seatbelt anyhow.
You mean 1kg? Cos DS is 17kg. If DD1 goes into the maxi rider, she'll be fine cos she hasn't cracked the 14kg just yet. But then my next worry is her outgrowing the height of the maxi rider before she's 3.. LOL