With ds we used a Mei Tei, which does both hip and back... we never wore our ringsling, he didnt like and honestly, I could never get comfortable wearing it. The Mei Tei was pretty good, but after hours of wear it really hurt my shoulders and back.
For this baby we got a sleepy wrap, which is a stretchy wrap, and most people say you cant back carry with a stretchy wrap, reviews about this specific one say it works really well for it. Actually that's a must for me... I love to back carry and read a TON of testimonials and looked at tons of pictures before I decided I trust this one.
I am 37 weeks preg and ds is 30 pounds plus he HATES being in a carrier at this point but we did try him in it, despite much protesting, and it held him just fine. Front and back... hip... you might be able to figure out how to tie it to work, I cant think of how.... sleepywrap.com and you can get 10% off with SIMPLEREVIEWS as coupon code