nice sling- the part where it's whipped is nice- much neater then i can manage- and actually is round and not square like mine
 
what type of cord are you using?

Now I got a little experience with those two slings.  The sling made with the 8" piece of safety belt is perfect for tennis balls.  The one made from a 7" is, as expected, a little small for tennis balls, but is still to long for golf balls. The little rascals simply roll off the side of the pouch when I load it.  For the golf balls to fit I`ll have to use a piece maybe as short as 6".  Or use longer whippings, but that seems like a waste of materials.
But it seems to be perfect for stones bigger than a golf ball but smaller than a tennis ball.
timann

Well, ilovepancakes, I am still in the learning phase when it comes to seat belt slings
 
My mother also had another strap in her garage, similar to safety belt, but not quite as wide.  I used some of it to make a 50" golf ball ultra sling.  
If it gives #me# some extra distance remains unknown
timann

I still haven't found any real seat belt... only a strap that's kind of like one.

now i know that someone here has mentioned using zip ties instead of wipping, and for a while now i have been looking some seatbelt to try it on.  
what i have here is not seatbelt but its some type of orange webbing.its not as thick as a seatbelt, so im not to sure of its durabilty,but it looks sturdy enough.
its to late to try it out, but tomorrow i plan to give it spin

Looks fantastic, I love the orange colour and the zip ties look very neat, as does the whole sling. As you say the material doesn't have to be seatbelt. I've used black nylon webbing of the kind used as backpack straps and a piece of load tie-down strap I found by the side of the road. It looks like cotton but it melts so must be some kind of synthetic.
 
My test for any new sling made this way is to put my foot on the pouch and to pull as hard as I can on the cords. I don't know how much force I'm applying, but it's got to be a lot more than they will be subjected to in slinging.
 
It has also occurred to me that using small hose clamps would be another quick and easy method of securing the ends. Being metal they may be a touch heavy, but they would be 100% reliable. I couldn't find any at the time and had since forgotten about it so have yet to try it.
 
PS. If you use the sling for golf balls and not abrasive rocks it will last a lifetime.

the whole thing seems very light, so i'm hoping that i will get the feel of the stones im throwing, better than with the leather split pouch that i like to use. i have a feeling that with the leather i used to make it was on the thick side..... the pouch has a weight to it that you can feel. not super heavy but its still there. with this webb-belt sling i'm betting that i can rely on the weight of the stone only, so as to judge when to release more accuratly