Optical trackballs don't work very well... They don't seem to capture well movements when you roll them fast (maybe they would if the ball was larger, the one I could get is shown below).
In the end what I did was increase MAME's setting to maximum sensitivity, to be able to go faster. Unfortunately that also made going slow slightly fidgety which made some parts hard to navigate... Worse than that, however, is that I obviously wasn't doing the maximum speed, which became rather apparent in a number of sequences:
1. Level 1, not able to jump for the extra points
2. In several levels, VERY hard to "beat" the enemy marbles (I usually was able to avoid them, however), which would give extra 1000 points.
3. Aerial Race has a steep ramp before a jump in the shortest route. It was EXTREMELY HARD to get to the top of the ramp without having the marble almost completely stopped.
4. Ultimate Race has a similar steep ramp near the Goal, which you can't take long climbing as it vanishes periodically.
Only after having a very hard time finishing it the first time (using save states) I tried the cursor keys, and that clearly showed me that indeed I wasn't cutting top speed most of the times. With the cursors, I could get 5k in level 1 from a ramp jump, push some enemy marbles with less difficulty, clear the Aerial race jump in one try mostly everytime, and easily climb the ramp in Ultimate Race. But I was too used to playing with a trackball, so I played everywhere else with it. Switching controls in midgame doesn't do wonders, but was the best control I could have given the circumstances.
For reference, the optical trackball I used was this one, which is obviously very poor for the job (I held it on the left hand so I could use it more like a regular trackball):
http://images.vnunet.com/v7_images/hard ... soft09.gif
Ivo.