I didn't know of any better way to get the ball to roll down the ramp other than to manually keyframe it every few frames to ensure it stuck to the surface of the ramp - if left to its down devices, Softimage would have simply allowed the ball to take the most direct route to the next keyframe - levitating the ball away from the ramp, or cutting straight through it, etc. This caused a few problems with the fcurve editor as each new keyframe places a new point on the curve, so adjusting the angle became a case of having to ensure that the curve ran continuously through each point. That meant a lot of handle adjusting and balancing.
It's looking really dodgy so far. I had trouble figuring out how to get the ball to accelerate on the ramp and slow to a stop at the end - it sort of does that, but it stops far too suddenly and the ball speeds up upon exiting the ramp. It should be easy enough to fix, once I've played with the curves a little more.