I would be concerned with dropping the ball. I'm not sure that claw will be able to squeeze it tight enough. Some drawer-liner will definitely go a long way in providing "grip" to your manipulator.
I'd also be concerned with such skinny pieces of wood being broken. Our manipulator last year stuck out less than yours, and it got smashed several times

. What we eventually did was wrap the wood with fiberglass; this made it very strong and it never broke again.
Just some tips to improve your design. Otherwise I think it is pretty slick! Good job CAD-ing your robot your rookie year! It took us 11 years before we did that!