[Dave]

Errrmm.... Ok... this could be less than good,
We put some white tape on the flexible coupling, mounted an optical sensor above it, and breadboarded a resistor onto the output diddly-boob. Anyhow, with the help of an oscilliscope, we found that rpm were about 320.. not a good figure. Also, there was a 15% difference between forward and revers, but that was sorta expected. What kind of rpm are you guys getting on the gearboxes, no-load?