That's a lotta car miles for a 21 mile hike! Glad you made it.
When I did that with friends, one of the hikers' partner dropped us off at Onion Valley after camping overnight there. And the week before, a friend drove my car up and parked it for us at road's end. So I guess it still took lots of miles of driving, but it was divided between three cars.
It's still a cool hike to start on one side of the Sierra and walk to the other in a day!
