Forgive my ignorance, but aren't lower PWM frequencies easier to do? I know there is lots of code out there related to servo control running at ~60Hz - I'd think that you'd just have convert from a "built in" PWM philosophy to a manually-programmed PWM where you program discrete pulses at a given length?
If I'm not mistaken, I believe the normal default setting for the PWM frequency coming from the Atmega chip is set at 5KHz. The Pwm frequency can be adjusted from there- using the programming software. It's just a matter of plugging in the appropriate numbers to the programming code.