I've been riding with just one pannier, the Arkel Bug, for a couple years now, without any problem. see http://www.arkel-od.com/panniers/bac...asp?fl=1&site= . It's designed to take off and use as a backpack and frankly until this fall I thought I made the wrong pannier choice because I almost never use it as a backpack. But I've finally made the plunge into almost-night riding home -- I ride home through the neighborhoods and on the bike paths near my office, then put my bike on a bus as soon as I hit the stretch of busy road, and that's the one time I find it handy to whip the Bug off and on my bike, and just throw her on my back for a short stretch from when I get off the bus til I'm on a long, climbing bike path again.

Punch line -- no problem with balance at all, and I pack that pannier with breakfast, lunch, papers, clothes, workout gear, you name it. You'll be fine with a one-sided load.

Marcy