Although the RPM will be equal on the Griffon's differential gear driven contra prop, it should be possible in theory at least, to have different pitches on the two propellers so the rear one could absorb more power.
I can believe that on push/pull aircraft like the Cessna Skymaster and Dornier 335 the rear prop would be in the slipstream of the front one and would thus need higher pitch anyway. Can anyone say if this is this also the case when the two sets of blades are right next to each other as on a contraprop?