Thank you very much for replying back to our questions. We decided to use the aluminum sheet. We will post pictures of our progress soon.
We have made a system to pick up the balls, but we have techinical difficulties.The picture below shows how the design of the picking up mechanism looks like:
http://img31.imageshack.us/img31/5907/img4665do.jpg
The problem that occured in the pick-up system is that even with the slightest push, the ruber bands move to one side and eventually tangle up. We were hoping for some ideas or suggestions.
On the bright side we have a shooting system that works efficiently:
http://img31.imageshack.us/img31/9587/img4667p.jpg
http://img39.imageshack.us/img39/6172/img4668v.jpg
We will post videos on youtube shortly.