First I added one 51V zener between flywheels and motor power, there was no change in the motor current from no flywheels/zener, which was a good thing, meaning it wasn't shorting out as before. It did decrease the motor "rattle" slightly and the FET temp slightly (about 5*F), not sure it's worth the additional 5 diodes. I also tried splitting the windings and adding a second zener, but no change from the single zener configuration. The flywheels and zener(s) are only barely warm after hours of operation. I might try some zeners with a slightly lower voltage rating just to see what happens with the FET temp then. I should also try the zeners to ground instead of motor power.

Jon