I had tried so many ring slings, but could never work any of them well. I decided I to stick to a front pack, but then I found the Premaxx baby bag which I loved. Ill still use it for DS2 on the hip when hes sick and insists on being held at all times. He's average size, not large, but the sling has no problems with him in it.
Anyhow, if you know people who have slings, see if you can borrow one for a day or two until you find what you like.