Looks good, eric. I love ingenuity like this.
I made one for mine that has held up for well over two years now, Holds +/- 100 cases before it has to be emptied, and is quick detach. It mounts with friction-fit pins and rare earth magnets, simply slides in and pulls out. Plastic frame, wire pins and a mesh bag.
"It isn't always being fast or even accurate that counts, it's being willing. I found out early that most men regardless of cause or need aren't willing. They blink an eye or draw a breath before they pull the trigger and I won't." - The Shootist (John Wayne)