Our team has a powered dumper. It has a tray with a slanted bottom, (like paint roller tray shaped) and the back wall moves forward to launch the balls forward. We can launch several balls at a time, into a trailer that we don't need to be directly up against. The balls come up through a trap door in the front of the tray. The only problem we had was that balls kept falling over the edge.
We were very proud of our design.