You're in good hands.....over the years I have met many groups hiking Whitney the way that you are doing it.
If I understand correctly, you hike with a day pack and the outfitter brings the rest of gear and sets up camp and breaks camp each day.
On the day before you climb Whitney, you hike to Guitar, the outfitter sets up camp and upon your return, the outfitter has taken the camp down and set up camp in Lower Crabtree Meadow. Correct, or something like that.
By the way, how many people going? And, if I am not prying, what is the cost?
Good luck
paul
