Recently replaced rubbers with silicone on my Space Invaders. Looks great as the leds transfer to the silicone, found that game speed up at least 30%, if the ball has a side spin happening when it impacts the silicone it will drive off in the spin direction at a great rate of knots. Sorry for photo quality.
They work great on ss machines but think damage may occur on dmds with the greatly added speed. Selectively placing may be advisable.