We used a double-roller, but it wasn't at all a pinch. It had two small wheels, the centers of which are slightly lower than the center of the ball, and they are spaced pretty far out. It gives the ball a lot of backspin, which gives us a lot of control.
I'd post a .jpg of the CAD drawing, but I'm at home and it's on my work PC... But I did post it somewhere on one of these threads already.
You can find video of it in action here:
http://www.facebook.com/profile.php?...=1212242513708