I cannot in good conscience recommend doing this without any suspension, at least not in the north to south direction. The climbs were fine with the rocks and bumps but the descents were very very very uncomfortable, and it took all strength just to hang onto the bars. It wasn’t a tire size problem, and you definitely can get through it on a gravel bike but your bones are in for a good rattling. The like 10 straight miles of descent into hobble creek canyon are pretty hard to get through. The route is awesome and the views are amazing, just maybe on a bike with suspension.