"I'm not anywhere near as sore as I thought I might be."
The Aucklander led for several days and remained in contention for most of the race, but in the end finished three hours behind American Justin Nelzen and two-time derby veteran Saskia van Heeren, from South Africa.
Nelzen and van Heeren ended the race only a few metres apart.
The pair finished at a gallop over the last 300-odd metres, taking eight days to complete the course, during which they had to change their mounts at horse stations around 40 kilometres apart.
They rode the entire race together.
Harris has represented New Zealand at top level at several challenging and physically demanding sports, including cross-country skiing, cycling and athletics.
"I'm in very good spirits and feel that, well, if it went for another couple of days I could certainly cope with it," Harris said.
"I have enjoyed the last four days in particular - the scenery has been magnificent."
Harris heads the New Zealand endurance team to the World Equestrian Games in Kentucky next month.
The derby is based on warrior Genghis Khan's postal system.