We car-camped in a campground along the Arizona trail by Colossal Cave (but one night I only used my backpacking gear). Then in the morning I packed it all up and did a fairly rigorous uphill hike in Saguaro National Park.
Good news: I can carry the weight good distances (maybe not thru-hiker distances, but that's another story). I can carry the weight uphill (which I've also been testing by doing things like hiking up and down Camelback twice and then up and down Piestewa without resting much). The weight (non-ultra-light as it is) doesn't seem to be much of a problem.
Bad news: My pad and sleeping bag aren't good enough for the cold that night (there was frost in the morning on many surfaces, even though it was forecast to be in the mid 40s). Hopefully the bottom of the Grand Canyon will be warmer when I go. But I'm going to need to invest in better sleep gear.