Russell,
First of all, Duke was asking if POLISH killed the cover, not sanding. He said he was told that POLISH, or the compounds in the polish, could alter the balls cover at the molecular level, irreversibly altering the ball forever..
Second, are you telling the people you're selling the balls too that you are changing them before the customer ever gets to throw them as Storm intended? What if a true OOB finish would be PERFECT for your customer, but they end up hating the ball because YOU altered the original surface without thr new owners knowledge and permission?
I'm not saying you shouldn't alter the finish, but the CUSTOMER should be the one to decide.