I have the Xplory set up with the carrycot at the moment, but DS is a very long baby and has almost outgrown it. He's only 13 weeks old though - can I put him in the seat attachment? I thought it was suitable from birth, but my instructions say from 6 months...but isn't the baby insert that goes in it meant so you can use it with a smaller baby, and it has a lie-flat position I think? Anyone know?