No, these speeds are not best case scenario. That's the whole point of the voltage drop from 1.2 to 1.05 per cell. As a matter of fact, see how my voltage drops from 29.6 volts to UNDER 21 volts when running my emaxx under extreme gearing?
Honestly, I gotta agree with sleepy23 - you got some problem with your batts, gearing, motor, or something.