The first four passes are generally steeper than the front section of Mt. Hamilton. There are a couple steep parts on Monitor but the highest grades are on sections of Ebbetts. None of it has extended sections like Quimby or Sierra. There were tons of riders on standard double cranksets. You could probably start off with a change to 12-27 then do both sides of Hamilton or Diablo from north and south and see how well 39x24 and 39x27 work over extended periods.

The altitude will affect you to some extent until you get used to it. By the time I was descending the back side of Monitor I had made the necessary adjustments to not climb in zone 5. The day before the ride was much hotter and dryer so I think we caught a break last year.