Woven wrap back carry- need help.

Forward carrying is very difficult for me to do for long stretches of time. My 6 mo love to be carried and wrapped up but i have not been able to get him into a back carry. I have carried my sister’s toddlers this way before and it feels so much better on my body. Ive watched so many video and tried everything i could find on the internet. My biggest obstacle is setting the seat, it has been impossible to get the seat to stay while I’m getting both tails over my shoulders. My baby will straighten out his legs every time or as I’m bringing the ends over my shoulders it will come out from under his legs and then his butt. Any suggestions? Also hair pulling is his favorite thing while I’m doing all of this.