I picked up a used #4 last winter. The critical section where the shoulder straps attach to the bag looked too stressed for my comfort. After breaking 4 upholstery needles and nearly spearing myself through i gave up.
One possible solution would be to ship the pack out to someone like   (You need to Login or Register  but with a minimum 3 week wait and shipping costs it's not a good option right now.
I swung by the local shoe repair guy; he got that thing under the sewing machine and went back and forth a number of times. It's a rock solid repair for a whopping $6.00 (cash only).