|You had it right - the square size made the file too big with the max dimension at 800. This file has the max dimension at 650 (other side 595) and it let me save at quality 4. It would look better if I hadn't had to save it twice as I didn't know you could not re-post the same file name. Lost about 25 kbytes on the second save to a new name.
Interesting learning experience.
Half Dome Side (4) RP