I did a credit card tour from San Francisco to L.A. in 7 days with a Carradice Nelson Longflap saddlebag (= 1200 cubic inches) and a Lone Peak H-100 "Alta" handlebar bag (= 600 cubic inches). You can find my approximate packing list here. I'm sure there are a few odds and ends that aren't on the list, though. As mentioned here, I could probably have fit everything into the slightly smaller Lowsaddle Longflap bag from Carradice.