Hi J.,
I am neither petite & my little guy has always been on the little side, and I found that when he weighed around 15-16 lbs, my back would get sore quickly. I own a Maya Wrap, which I like OK, but if I had another child, I am certain I would try the ERGO from the beginning. I keep hearing how you can carry a child up to 40 lbs. & that it is "easy" on the back. With the Maya Wrap, I still get sore sometimes & feel like I am always having to mess with the tail, make adjustments, etc. My guy has always been on the small side, so when he was very young, it felt like he was getting lost in the sling. Even now, in a side/hip carry position, I feel like his little bottom is so small that I have to readjust him frequently. He's 17 mos old now & about 22 lbs and VERY active, so carrying him around is not much of an issue these days. Other moms I know of slightly older toddlers who like to be carried a lot do use the Ergo successfully.
Good luck!