I really have to take a pic of my setup and post it... I use a backpack strapped to my rack... the biggest issue is that I have to make sure I put an extra strap around the lower rear corner of the bag and tie it off to the upper front corner of the rack to keep it out of my wheel.
Been carrying my laptop that way for weeks... it works GREAT.
BTW: It's difficult to find a pannier for a reasonable price that will hold a 17.4" widescreen laptop.
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"There is no greater wonder than the way the face and character of a woman fit so perfectly in a man's mind, and stay there, and he could never tell you why. It just seems it was the thing he most wanted." Robert Louis Stevenson