i finally got those elusive and expensive phil wood bb cups today. i went to install the old un72 bb and even when the cups were tightened down as far as they would go, there was still play. does anyone know if there are different shell sizes used with the un72? mine measures about 57mm. i saw one on ebay just now with a 73mm shell. i assume that's what i need. can someone tell me if that one (the 73mm shell) is the one i want?