I disagree that everyone using 70 q panniers will fill them with junk, thus they will be heavy. I have 70 q panniers and just got back from 2 weeks in Colorado. For the bulk of the time they had a lot of extra room, but a trip to the grocery store and the fact that I like being able to put my cycling shoes in a pannier while walking with the bike was a huge plus. I actually against having panniers with only one compartment (sort of the same reason that I would not put all of my kitchen wares into one big box in my kitchen and have to dig for silverware, bowls plates etc...) I prefer to limit digging for stuff in my panniers. I don't think you need such waterproofing that your gear will stay dry even if submerged under 20 feet of water ( I am not familiar with such waterproofing needs with bicycle touring) Having many pockets outstrips the need for waterproofing by a long shot.