I thought about this, but in the end I didn't find any useful measure for the speed, as the actual movement speed of the servo is unknown. 50% or 1% wouldn't match the reality either, so I just went with one byte speed indicator as compromise between data overhead in the Servo-library, processing overhead in the interrupt function and granularity for the speed regulation. It was good enough for what I needed - lowering model aircraft landing gears in a realistic manner.
Korman