The front and rear slipper out-drives can slip independently of each other as they are not physically locked together.
They are held together by the screw, thrust race and spring assembly that runs through the centre of the slipper.
Think of it as a diff assembly but with no balls, just plates of friction material.
If you hold the front wheels of a car with the 'dual slipper' in you would still be able to rev the car up without it trying to smash you in the face, the rear wheels would still turn.
For most normal applications/tracks, the standard pads work fine on both front and rear. you can however tune the slip characteristics by drilling holes in the pads (reduces surface area) and since the pressure is constant between the plates then.
P=F/A => F=PA
Reducing area reduces the force applied to that 'end' of the drive line.
Typically, we have found a good balance is to drill a standard pad with 6 x 2mm holes equi-spaced. This works well on slippy floors where drive to the rear needs to be controlled.
Also, keep an eye out for different pads
