Have an inclined ramp that points downwards, make a device that is automated and launches the steel ball with the same force every time, and then measure how far the ball goes.
Or, you could make the automated launcher powerful enough that the ball would go over the edge of the ramp, then it wouldn't need to be downwards and it would be a perfect way of testing the SMOT for anomalies.
Make the magnets on the sides of the ramp removable.
Remove the magnets, without changing anything else in the experiment.
Measure how far the steel ball goes.
If the steel ball travels further when the magnets are added, the OU effect is undeniable.
You may say, then how come the SMOT can't close the loop if it's truly an anomaly?
Well lets say you tapped an energy source that can only move tiny dust particles a few mm. Would you expect to use that energy source to power a perpetual motor? No you wouldn't.