Yes, if you want to set up a tent in the Grand Canyon, you had better request permission months beforehand. Fortunately the weather is very predictable there.
What I did was renew my fitness centre membership in January and start working out on the Precor EFX544 crosstrainer four times a week, 30-40 minutes each time. I hoped that this would make me fit enough to carry my backpack out of the Grand Canyon.
Here is what I packed. As you can see the 1.5 duffel bag requirement was met (plus a stuffed knapsack as carryon luggage).
Why so much stuff? Well, the agenda for the trip had so much variety that we took a lot of things that we would be using at most one time, but that were still totally essential. Like the ice axe and crampons.
As it turned out, one of the eight people who were going dropped out at the last minute so there were only seven of us for the two vehicles. Our stuff barely fit. We had to spend quite a bit of time packing up every day.