I was basing the "ideal" voltage on the 32 x Square Root of inductance which, in the case of the cnc4you steppers would be 55v. The information on the Gecko website seems to infer that voltages above this "ideal" will just produce more heat through iron losses with negligeable torque gains. If you guys are using 68v without issue that would suggest the mathematical "ideal" and the real "idea" are not one and the same thing :)