When my son was about 6 months old, he'd gotten too big to be carried in a pouch sling across my chest, but we were having trouble shifting to a hip carry. I would get him in, make sure he was seated properly and everything was cool until he got excited about something. He'd start to jump up and down until he popped his butt right out of the bottom of the sling. He never fell, but it made me stick to wraps even for short errands a lot more than I wanted to.
I decided to make my own ring sling that would hold him in there no matter how much he wiggled or squirmed. As an added bonus, I discovered that by wrapping the tail of the sling between his legs and across my back, I had made a sling that took some of the pressure off my shoulder. This meant I could hold him much longer in this sling than I could in standard pouch or ring slings.
This video below demonstrates our sling. If you choose to make one yourself, I used about 3 yards of fabric for mine; you may need more or less depending on your and your baby's size. The rings are sewn to spread the fabric evenly across your shoulder for extra comfort, and I doubled the lightweight fabric over itself for extra strength.