I will be doing the North to South rim to rim hike in MAY. Last time I hiked the Grand Canyon (South Kaibab down..Bright Angel up) I had to take a smaller external frame pack than I usually use. We were able to fit 2 empty packs in a large suitcase by just undoing the top (internal) support wires. I am currently looking for an internal frame pack for my upcoming trip.
-Will