DS is nearly 5 months and is a chubba bubba. I am using bjorn carrier just now which he loves but it is killing my back. I have an Ergo that I used with DD for ages and I love it, places LO's weight mainly on hips not back so fab for me and DD was also very happy in it but DS much prefers to face out. So bascially I need something with similar design to Ergo to lessen backache but where DS can still coo at all and sundry - any suggestions? TIA