I have the new Classic Ceramic coated platter. It does indeed have a shallow label sized indentation on it. The platter is totally flat, except for this depression.
I have found that the rubber mat does nothing for the sound. I use the one piece clamp, but found that it does not work properly with the mat. Without the mat the record edge tends to rise a bit when the clam is applied. Makes sense since the clamp is pushing the center of the record down into the shallow depression.
Best for me is to use the rubber washer and put the clamp on lightly (not too tight).
I have found that the rubber mat does nothing for the sound. I use the one piece clamp, but found that it does not work properly with the mat. Without the mat the record edge tends to rise a bit when the clam is applied. Makes sense since the clamp is pushing the center of the record down into the shallow depression.
Best for me is to use the rubber washer and put the clamp on lightly (not too tight).