To Kick:
Yeah I had been making slings with knots that poked through the leather and were held in by friction at first but as I got better the (G-forces I guess?) started straining the leather and the knots would pop out, so I used a similar set up to that which you'd use to attach rubber flat-bands to a slingshot pouch, and you are absolutely right, the release is much smoother as a result.
To Kilisi:
Thanks very much man! it's taken a while but I'm starting to get better at making the look nice and work well!
To Mersa:
I've tried two strips of leather, and narrow short pouches, and narrow long pouches, but the classic slingshot style just seems so versatile and consistent! also thanks!
To Morphy:
Oh no way my dude, this is like my 20th attempt at sling making ahahah I probably worded my title badly! Thanks man!
To Joe Meadmaker:
I have been running single strand paracord slings for almost the whole time I've been learning, they were fine for ages but as I've gotten better I think I'm slinging much harder now and because I use a primarily underhand swing and make a big effort to get my shots as low to the ground (usually about 20cm and straight as possible the knot end of my sling is probably taking big damage as it whips the ground about 100 times a day, I know this as my current braided sling takes chunks out of the sand and grass when I sling.
Also, the heavy cords feels more powerful so there's also that.
Thanks to everyone again!