my tri bike has a 11-25 rear and compact 34-50 up front which i guess in theory isn't bad for climbing but i guess the geometry of the bike makes it a little hard (i also ride a good 5 inches of saddle to areo bar drop). The specialized does have a 12-25 but it is a 52-42-30 triple.
How much would a 11-28 help compared to a 11-25 and can you pull it off without changing derailer (short cage ultegra 6700) or chain length?