I've been using the Vario rack successfully for carrying my backpack. Velofred's site says the maximum load is 5kg, but my rack has 7kg stamped on it. I weighed my backpack in at 12 pounds, but this semester I didn't need to carry any books, so I'm curious to see if it will be ok if I add another 5 pounds worth of books.

http://www.velofred.com/product_info...roducts_id=586