I have a really bad back (I'm 6 foot tall, have a broken tailbone and recenly had a back injury from the eppidural I had for my c-section)
I have had a lot of luck w/ the Moby Wrap and a carrier called Babytrekker. I'm shocked to say but I've also had a lot of luck w/ my Ella Roo ring sling. IT's just that it has to be worn the right way. Make sure the fabric is spread out over your shoulder really well, and the fabric is opened up really wide across your back and make sure the fabric goes right up as high as possible under your other arm. When you look at me head on there is a perfect line from arm pit to arm pit. I also only carry baby facing me and upright, centered on my body. I also make sure that I adjust it really well so fabric is really well fitted and keeps baby really close. When baby sleeps I tuck his head in the fabric, when he's up he pops his head out and looks around. HTH