Does anyone know if the newborn pods are fairly universal? We have an uppababy vista for use most of the time but its too wide for my parents front door. We have a joie brisk travel buggy that lies flat and is suitable from birth but have been looking at newborn pod/cocoons to make it a bit comfier/cosier. As they all work with 5 point harnesses I was hoping they may be fairly universal if the right width?