A question on the required wilderness permit to backpack from Horseshoe Meadows and exit via the Whitney Trail:

-Background: I'm trying to plan a "Whitney thru the back door" trip for this September, coming from Horseshoe Meadows (possibly taking an extra day to summit Langley, too), via Guyot Meadows and Guitar Lake, up to Trail Crest, side trip to summit Whitney, and out with a Whitney exit permit. Sounds reasonable, and I've read that's some very pretty country.

I tried going through the recreation.gov site to see how to set this up.....I can find the Long Lake/Cottonwood Lakes area part of the permit easily enough, but the remaining nights (which it asks me to specify each one) are not in their dropdown list at all, and when I try to specify "Mt. Whitney-exit" (like the Wildernss Permit page says), I don't find that in the dropdown for the exit point.
What in the heck am I doing wrong here?

Help?

Lewis