[JesseK]

In our sandpaper tests (well, skateboard grip tape), even rolling the ball on top of the sandpaper produced enough wear on the cloth of the ball to warrant us not using it since that directly violates a rule -- no need for a Q&A there. It's the same damage one might see on cotton clothing that's years old -- little bumps of fibers. In our Velcro tests neither side of the Velcro stuck anyways, so it didn't matter.

There's a rubber mesh, the stuff used in VEX, that has a decent amount of friction with the ball when there's the right amount of pressure/tension. We're prototyping ways to manipulate the ball with it tonight. If used in a conveyor system, we'll probably glue sandpaper around a rod, then use that to turn the inside of a rubber mesh 'belt'. The sandpaper wasn't abrasive to the rubber mesh when we 'rolled' it over the mesh.