I'm having a bit of an issue trying to figure out if these panniers will work on the rear of my bike. They are listed as being for children's bikes and front racks. I want a modest size pannier for my rear rack. My Cannondale Contro-e Speed says the rear rack is designed for the Ortlieb QL-3 system. These are listed as being QL-1. From all I can tell, any of Ortlieb's systems will work on my rack. Does anyone have any experiene with these? I'm trying to wade through the mirada of Ortlieb's options.