I would truly like to do a rim-to-river and back in one day. I'm incredibly impressed by your adventure!!!
I would have to seriously train for it (like I train for an Ironman, tho). I don't know what would be better: getting all the soreness over in one day, or letting it fester overnight and then starting back up the next day??? Rim-to-river and back is the next hike in the canyon. Or even better- a rim-to-rim from the N to the S rims. That sounds even more fun!
We encountered about a half dozen canyon runners on the trail heading up- spaced out over lots of miles. I was duly impressed. I can't imagine running down those trails: so rocky and ankle-breaky- especially since I know a lot of them left the rim before daylight broke and there was ice the first half mile of the trail coming down. WOW!