motor running voltage for Electrocraft E670 -06

I measured the terminal resistance of the E670 -06 motor and found it
to read 5.1 ohms. This would place the coil resistance between the
suffix -03 and -04 versions or half the resistance of the -05. Can I
assume that if the -05 version needs 152v to achieve full performance
at 10 ohms the -06 version would need half the voltage or about 75v to
achieve its peak performance?