I too have an archery background used to do field competition. As for slingshots while normally I have used more modern slingshots I have experimented with materials and made some traditional slings. While you can use cord leather thong material is better. It is stiffer and you really need that. While they are tricky to learn to use once you get the knack they can be surpisingly accurate and generate a lot of force on the projectile. What to use for a projectile seems impotant as well. While with modern slingshots I use lead shot you seem to need more mass with a sling so larger ballbearings or rounded rocks is what you have to go with.