Making slingshot questions?

My father made my first slingshot out of a tree branch. He used rubber bands and the tongue of an old shoe to make the pouch. I used rocks and I won't tell you is was accurate...probably because I never really practiced enough. Now, surgical tubing is excellent. Take a length in your hands and see how far it will stretch. Basic length of the tubing, at rest, would be around six to ten inches, depending on how long your arms are. You can attach one end of a piece of tubing to the frame and the other end can be attached to a piece of leather...about he size of a shoe tongue. Yes you could use a continuous piece of tubing and slide over it (before fully attaching to the frame) a piece of leather as a pouch. Have fun.