Something we have noticed about the orbit balls is that they are very springy.
If you choose to use a belt, it should be set up in such a way that it applys a good deal of force on the ball to lift it.
If your belts are too springy the balls will slip when they reach the median point between the rollers.
We've been considering using a single high tension belt, like what many teams use in their treads.
This pic , from team 45's '03 bot, is what we really want to use. Does anyone know where they got it? F.N. Sheppard, Bercoflex?
F.N. Sheppard also has these really cool "profile" timing belts that could be used as scoops to lift the balls (instead of rolling them up a channel).