Above is an 11" square target, or a catch to sit behind the target. It stops the steel balls and keeps them contained so that my cheap ass may re-use them. It works pretty well, although the fabric has already started to tear around the grommets.
Kangaroo leather is supposedly the best for pouches, but it's very expensive. Thinking cow leather would be good enough, I made a pouch of some about 1mm thick. It tore at the end holes a little too much for comfort. I came up with a knot/stitching pattern with the sewing awl to reinforce the holes. So far the pouches with stitching have worked really well.
Smaller pouch, for 4.5mm bb's:
Fir slingshot ready to shoot:
I also made this fixture for attaching the bands to the pouch: