I would suggest the houdini stop Houdini Stop car seat chest strap It connects to each strap of the car seat with simple mechanisms that can be done and undone with one hand. Its been crash tested in Australia and has been approved by the ACRI. We bought one for our 2yr son who no matter how tight we done the straps he would always wriggle his arms out of there. This piece of kit stopped the little escape artist and have no problems since