We have these (i think 15l each) on a spartan front rack on our Terns and they work fine for us. I don't worry much about the bottom clips though Keri tries to hook them on more. We're mostly on road or going pretty slow so bouncing around hasn't been a problem. Sometimes put them on the rear - need to adjust them so heels don't hit and then they're fine, but i quite like the weight being on the front. Btw, Keri is using using Arkel dry-lites on the rear and likes them. (The bottom clips for those is too low so she tends to put a bungee right around the middle of each bag and the carrier leg).