Heinz Kegler, because an infinite number of factory servo clutch inner drums was not available and in fact limited to a handful, found it easy to take a regular clutch outer drum and grind an angle into it. In fact he offered this service along with his work on brakes, setting up clutches and manufacturing his swingarm collars.
Because the torque is not the same as it is at the outer drum far away from the center as it is closer to the center of the clutch, putting the same angle in would help but might not have as much servo effect.
Heinz said it took a lot of trial and error to get the exact right angle for the inner drum, too much and it would not release, too little and it would not clamp hard enough.
Of course opening up the slots to an angle means they will be wider at one end than the other, but they naturally line up against the side that drives them so it is not an issue, they are not rattling back and forth causing any trouble.
If someone is patient laying it out and altering it either with hand or machine tools, it might be a nice project for the bored Dominator enthusiast with an extra clutch laying around to play with.