Just sharing my experience. Many panniers are smaller on the bottom than on top. I don't think many of us has experience with this type of bag. I did not. During riding the contents will bounce around and go further and further down the bag (the funnel) until they are all tightly squeezed on the bottom. Maybe this is good for camping. But hardback books, paperback books, notebooks, phone, iPad, laptops, calculators, papers, work stuff, will all get scrunched and wrinkled. Book covers will get dented and dog-eared. Clothing should be packed on top or they will be super wrinkled. I am not much of a camper anymore and I use the panniers mostly for work. I would definitely get something with a square bottom like a grocery bag-type pannier to keep my laptop and papers from getting scrunched.
Panniers are like rock tumblers. You put a bunch of stuff in and over the course of a ride they all tumble and shaken. Your keys will scratch up the camera exterior. The phone will scratch the laptop etc. The loose fork will scratch up your food containers. The extra battery will scratch up your headlamp. Even a wrench or socket set, unless tightly packed, will come out looking well used. Lots of people do it but be careful when packing to avoid this. You will soon learn.
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