I am curently riding my Litespeed Tuscany set up with a compact crank and a 11-23 cassette. I ride around the central Indiana area where the terrain is somwhat flat with a few hills. In about a month I will be riding the Old Kentucky Home Tour out of Louisville. The ride has a lot of hilly stretches and I am looking at installing a larger cassette. Any recommendations as to the cassete size would be welcome.