On 8/15/16 at 6:32AM I finished a Yo-Yo of the HST from Crescent Meadows to Whitney summit and back. I believe this is an Eastbound FKT as well as a Yo-Yo FKT.
Total time was 44 hours and 2 minutes - 20:06 to Whitney summit and 23:36 back to Crescent Meadows, with 20 minutes spent at the summit.
I started at Crescent Meadows at 10:30am on 8/13, arrived at Whitney summit at 6:36am on 8/14, left the summit at 6:56am, and arrived back at Crescent Meadows at 6:32am on 8/15.
[edit 12/4/2016: Original GPX files were sent to Peter Bakwin and Adam White for verification etc shortly after this trip. Adam combined the two files into one GPX file and using programming magic, added data points exactly halfway between each existing data point in both time and space, in order to increase the accuracy of the Strava data for per mile pace etc as it was wildly inaccurate in the original files due to the 1 minute GPS sampling rate I used in order to preserve battery life on my GPS watch. New Strava link below is to the combined file with additional data points.]
I used a Suunto Ambit3 Peak GPS watch which was set to record at 1 minute intervals, to ensure that the battery would last the entire trip. As a result the data produced by Strava for moving time, pace for each mile, etc was wildly inaccurate, [edit: now somewhat more accurate] but the total time is correct.
Full report to follow after I get some sleep. I did not carry sleeping gear and did not sleep for the entire trip. This was my first time on the HST, although I have done the JMT section from Wallace creek to Whitney a number of times. So I guess that makes it an Onsite, Solo, Unsupported, Yo-Yo FKT of the HST. The second half definitely turned into a death march but it was worth it to avoid descending the Whitney trail and the dreaded car shuttle!
Just for reference: according to Sierra Mapper, the total elevation gain on the HST going from west to east is about 18K feet and going from east to west is about 10K feet (add another 6,000 or so if starting at Whitney Portal). So the total elevation gain for a Yo-Yo is about 28k feet, compared to about 36k for a full JMT from WP to Yosemite. [Edit: Strava says about 20k feet of gain, not sure which number is more accurate but likely the truth is somewhere in between]
[This post edited 8/16/16 to add Strava links and precise times after doing some calculations from GPS data, and to add the link to the trip report below]