The ServoCity/Lynxmotion timing pulley is a reasonable "fall back" choice, but there are much better ways to go if you really want a well engineered end result. For a start, it's an MXL profile, which is far from ideal, not designed for precision bidirectional positioning - it introduces its own backlash to an already backlash-happy servo. GT2, GT3 and HTD profiles are a much better bet. The difficulty is always attaching gears/pulleys to the servo. Two general ways: ServoCity's
shaft attachment (several sizes available) which allow you to fit a plain-bore pinion gear or pulley, and a round servo "horn" (
http://www.servocity.com/html/servo_hub.html or Futaba/Hitec originals) to which you can bolt a pulley/gear (which has to be accurately drilled).
Backlash is THE big enemy - in gears/pulleys but also in bearings. A timing belt may mask the unconstrained rotation ("lost motion") that is the symptom of backlash but it can never remove the
delay and the
kick which occurs when the transmission train reverses direction. Zero backlash is one of the
big reasons the Zenmuse is so effective.