[Liu_yiang]

3 things to think on:
1.Bumps are going to be nasty, requiring that you let go as you go over.
2.The ball's going to need to take more that a few hits, and if a robot were to, say, hit the soccerball, would it be able to still hold on?
3. Once you've got it, how are you going to shoot it? If you plan on having a light grip, #2 comes in. If it's strong enough or too strong, you'll need to let it go before you hit it, meaning it may roll.

We haven't gone through the gauntlet of design ideas, but it seems suction hasn't stood up to testing.