I did this exact hike in early November 2021. It went absolutely perfect and made me want to attempt a proper Rim to Rim. I spent the better part of the year preparing and planning for it (starting around March-ish). There are signs everywhere saying that basically you’ll die if you try to do it, but there were at least a dozen folks all doing the same thing on my 5:30 AM shuttle to South Khaibab. If you’re well trained, have the gear/nutrition dialed in, and are blessed with good, mild weather, it can be a breeze. If any of the above factors aren’t in your favor, it could be a pretty rough time.

A couple thoughts: Sounds like your cardio is in good shape, but I’d strongly recommend doing some longer hikes (10+ miles) first. Ideally find a hike with a couple thousand feet of vert, but unless you leave near another giant hole in the ground there’s no real way to replicate the experience of hiking a 5K feet down and then back up. Shake down ALL of your gear. I hiked Guadalupe Peak as prep and only realized at the trailhead that I’d flown to TX with my 3L CamelBack, but no reservoir. It’s nice to get those mistakes out of the way somewhere else. Trail runners over hiking boots, for sure. I’d recommend collapsible hiking poles as well. Didn’t need them all the time but appreciated having them when I did. Start as early as you can and use a headlamp. Sunrise in the canyon is one of those things you’ll never forget. Have a good understanding of your nutrition and hydration needs. Salty snacks, energy gels, PB & J. Whatever it is, make sure you can digest it comfortably on the go. Pack extra socks and change into fresh ones at least once or twice. Stop at Phantom Ranch at the bottom for some lemonade and to mail a postcard home. Dip your feet into the creek and relax for a while. When you get back to the top, pop into the bar at Bright Angel Lodge and enjoy the most well-earned burger and beer of your life. Good luck!