I made these feet for my Rostock printer because I had an LCD interface that put the height of the Arduino / Ramps boards taller than the motor ends. I screwed them into the M4 holes on the bottom of the motor mounts and then added a felt pad to the bottoms.

Print six of these (or three if you want). Use M4 screws to screw them into the holes on the bottom of the motor mounts. For extra cushion I added felt pads to cover the screw ends.