One really attractive feature of the HST is its built in acclimatization. Unless you are really blitzing it, you will only go from about 6500 at Crescent Meadow to 8300 at Hamilton the first two days. Hamilton is lower than Whitney Portal. Then to about 10,700 at Kaweah Gap on the third day, and right back down into Big Arroyo. Unless you hang around Precipice LAke, Nine Lakes Basin, or upper Big Arroyo, you don't even have a really high camp until you climb out of Kern Canyon a few days later. Your Highest camp before then will likely be Moraine Lake at 9300. So you have plenty of time to work up to your 11,000+ camp around Guitar.
There is frequent water along most of the route, with two exceptions. First, There is NO WATER at the Crescent Meadow trailhead, and for the first few miles, which is of course also the hottest segment. Fill up and drink up at the Giant Forest Museum area before you go in to Crescent Meadow.
Second, You should expect it to be bone dry from your Guitar Lake Camp to Trail Camp. Two litres each is below the usual recommendation of 3. I would at least take an extra quart zip lock bag (to be consumed first) for this stretch.
Another interesting strategy on this trail is bear canisters. Check the rules on this, but as of last year, they were mandatory only in the Whitney zone, and recommended on the rest of the trail. If you camp only at established sites, you can use the food boxes all along the trail until Guitar, where there are none. This means you can use smaller or fewer bear canisters, taking only what you need for the last couple days food. Double check this, as some boxes on the JMT/PCT are reserved for JMT/PCT through hikers, but if you plan right you should need less than half of your food in canisters.
Oh: the bears know the difference between you and food.
In certain places, such as Hamilton, the marmots and deer will be more of a problem than bears. Deer at Hamilton will go after anything salty/sweaty: hiking poles, clothes, wallets.
Have a great trip
