Although I haven't ridden very far with it, I have an Osprey Talon 22 which is pretty popular with the "bikepacking" crowd. It doesn't move around, and has an airgap to keep back sweating to a minimum. For those who haven't heard the term bikepacking, it's basical a type of touring/camping done off-road on mountain bikes and most ride without racks. All gear is carried in large seat bags, frame bags (mounted in the center triangle), and handlebar bags, and backpacks. This leaves the bike more maneuverable in rough terrain than rack/pannier setup.