Wow. Sorry if I sounded harsh. I was in a bit of a grumpy mood yesterday. I do know that Heifetz told his students that they should either learn to play w/o the shoulder rest or else drop out of his master class. Also, all of the great violinists I know do not use them. I would imagine that a cushion would take away much more than a rest, but imagine those soft rubber holders on the rest squeezing the sides of the instrument enough to hold them there. Also, extra force is added to reduce the sound when the player pushes their head into the chin rest, thus pushing more on the shoulder rest and having even less sound.
I usually just dig the tailpiece into the middle of my neck very hard.
