--Repeated the tick count over known distance drive experiment from 10 Jul to see if the change in hardware (different USB hub, different cable arrangement) had an effect on the ticks/cm measurements.  The new tick counts are LEFT = 328.288 ticks/cm and RIGHT = 323.709 ticks/cm.  Measurements were taken from 5 runs, varying between 15.66' and 68.38'.  R^2 values on both linear regressions were > 0.999998, so I'm confident that the linear fit is good and using ticks to measure cm traveled will give accurate numbers.