If you intend to use your back (and your neck) in the future....I'd say, yeah - 20 pounds on the pannier would be a whole lot better than on the back. That's a lot of weight. The Arkel commuter bag has a laptop sleeve, and can carry a boatload of other stuff along with it. Clicks on and off a rack wicked easy, and you can cover the hooks and - viola - an incognito pannier disguised cleverly as a carry all tote.