Thanks. I would say it all depends. A few years ago, before my knees and body started falling apart, I did lots of difficult climbs in Colorado with a compact on front and 11-28 cassette just fine. But, three knee surgeries later ... we'll see. I think I'll start a bit lower, with 32T, but having this derailleur will allow me to expand that if I need to. Perhaps I should leave extra slack in the new chain to go bigger in the future if I need to?