Most people who want to ride the Graveler and don't are stopped by the calendar, not the miles. Half-Grav exists for them: you get the camp, the towns, the food and the music, and you are back at your desk sooner.
Half-Grav is built so that the shorter week still contains the day everybody talks about — the low road into Helena on 8 October, and the King Biscuit Blues Festival with admission included. The evenings, the food and the towns are identical. You are doing the same event, for less of it.