Ready enough for the Grand Canyon

Mark and I have a Grand Canyon hike scheduled for April 24. We'll be doing our usual route down the South Kaibab Trail from the South Rim to Phantom Ranch and then back up the Bright Angel Trail to return to the South Rim - a total of 17 miles (oh, yeah - and about a vertical mile each of descending and climbing). With that in mind, today I hiked 12 miles in 3.5 hours: 4.5 miles flat in Spring Canyon, then 7.5 miles on Cowles Mountain - 17:30/mile average. Kinda gimpy but good enough.