I found out a couple of things that helped.
First, I adjusted the wrap to fit higher on my torso. That helped with the back pain.
Second, there are more than a few ways to wrap the fabric around your body. You can bunch it or lay it flat. First time I bunched, this time I flattened…flattened = better.
The walk was easier even though it was still friggin hot! I did adjust the “sleeves” of the Moby wrap on the way up the hill and it was more like a tank top…better. But I’m sure when the mornings get chilly, I’ll appreciate the sleeves.