Just acquired a very lovely 2014 Specialized Roubaix Pro SL Dura Ace with an 11-28 rear cassette. I know 28 is the maximum size specified by Shimano for this groupset, but equally I know one can usually easily run a few teeth above the official limit. Just wondering if anyone else has run a 30 or 32 tooth big cog on Dura Ace of this vintage? Any advice much appreciated.