Thanks for the helpful information. Our hiking permit is for a Saturday and I was able to get a camping permit for Thursday night so it doesn't sound like there will be too much difficulty getting a walk-in camp site for Friday night since we will be sleeping there the previous night.
Regarding my problems with reserveusa.com, I tried many variations on my web browser (tried 4 different ones on 2 different platforms!) with no luck. Finally I ended up calling them and this worked flawlessly.

So much for technology!
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