Excellent, thanks for the info! If they can hold the permit until 2 or 3 in the afternoon, that will really help. I'll give them a call the day before.
Yes, I'll definitely release any unused permits if my plans change. Frankly I was surprised to get a permit reservation at all - I was prepared to do the walk-up permit lottery thing, but then I saw on recreation.gov there are still many dates open for the summer, if you're a small group and willing to go mid-week.
I agree doing the day hike without an acclimatization day will make it tougher. If I can finagle it, I'll try arriving in the area on the 19th instead of the 20th. I survived two prior Sierra 14ers fine without an acclimatization day, but they were both two-day climbs instead of a day hike.
