My Creature worked great on mediums.  It is a very smooth rolling ball for me.  I did not get many games on mine since I switch my pitches after I drilled it and have not gotten around to replacing it yet.  It was a great ball to pull out of the bag with a fresh pattern.  I did not get a chance to mess with the cover on this but would imagine you can take the surface down and make it a little stronger.  I have not had any problems altering surface on any of my 900Global equipment.
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Derek Trowbridge
900 Global:No oil pattern we can't tame
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