FYI - Frequently, there is a ranger at Split Mountain checking groups on the way off the river. And sometimes, while on the river. We have been visited at Jones hole.
The group that launches together is expected to run the trip together. I was on a trip a few years ago where they had issues with a kayaker that got to the takeout a few minutes ahead of the group. Guessing a 24 hour difference would cause even more concern from park officials.
"Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover." - Mark Twain