All of this has been interesting and educational, mainly because of Barrettscv's input. I shall have to revise my prejudices against cross-chaining. I still think it is inelegant, though, so irrespective of its effect on chain wear I shall continue to avoid it. Notwithstanding your psychological benefits of climbing in the big ring, Hermes, I don't think I'm going to be able to persuade myself that the 53-25 is really much different to the 39-18.