I can see the advantage of the Clarkson specific type, i never said they slip!
The runout would or could have been before my time, dont know whether spindle, or Clarkson shank, nut or collets were out. Set up like you say backing off around 1/4 turn. The point i make here is, whatever runout there is due to extra additional parts with subsequent machinings, amplifies the further out the spindle the cutter is.
My actual grievance is the time it takes to change a cutter.