My heels hit my panniers. It's really annoying, but since they're just soft nylon panniers it's not going to tear up my ankles or cause me to not have an OK pedal stroke. I wish I could adjust the placement of the panniers a little, but alas, they're single piece sling'em-over-the-rack 80's vintage panniers. They were free, so I don't crab about it too much, but I'm still looking for just the right pannier to actually pay for. They're all either a little too small or designed for unsupported touring and therefore gigantic.

When I was in middle school I had one of the earlier hybrids. It had a rack, and I had a bungee with two flat cords. The rack itself had a "trap", a hinged thing that worked great to secure the previously mentioned nylon panniers. But when I needed that extra carrying capacity, I just bungeed a milk crate to the rack. In hindsight I was really glad that bike had a step through frame the way most of the European and Asian everyday bikes do. It worked remarkably well.

Today I frequently use the same panniers and then use a small cargo net to strap my backpack to the rack instead of wearing it. I hate wearing a pack as I ride - it makes my center of gravity seem too high. And I've yet to find a messenger bag that sits comfortably, doesn't twist around and doesn't squash my boobs to all hell....