I did that route last August but stopped at the tarn above Guitar prior to going up. The time from Crabtree to Guitar was about pretty short, but I can't remember the exact time to get there. From Guitar it was 3 hours to Trailcrest with packs and almost 2 hours from there to the summit without packs. We dropped our packs at PC as we exited via the Portal. You should consider leaving the Guitar area with 3 or 4 liters of water. Everyone is different but I drank a lot during the trip. You could stash a liter at Trailcrest to pick up on the way down. But past TC you have no chances of getting anymore water. Also you may want to leave your tent open as the rodents have been known to crew through doors to get in. Even if in nothing is left in the tent. The hike from the PCT to Whitney is far easier then the 99 switchbacks. I think once you get up there and the switchback start, coming from Guitar, there's only about 9 or so before you hit TC.
