We're riding in late October, which should be a significant help in terms of staying hydrated. I'll still probably bring an extra bottle like you did... part of me thinks my osprey hydration pack would be a good addition, or maybe my dinky little camelbak.

How did you like your seat bag anyway? Do you know what the difference between the backcountry model and the expedition model is? Was it solidly attached? ( I read a couple reviews that make it sound insufficiently supported.)