Beautiful route, with wonderful views of the Valtiberina, the views on clear days range up to the Sibillini and the Gran Sasso. The only flaw is the central 2 or 3 km that I would define as gravel extreme bordering on enduro. It's a shame because from Montemercole onwards the surface is also spectacular. Be careful in case of recent rains, the central km become practically unfeasible.
Nice connection between the Alpe and the Libbia pass. Some points are pure MTB, it really takes skill to do them on gravel without putting your foot on the ground. Luckily they are only sections, interspersed with sections of smoother trail. With a frontina you definitely have more fun but even with a gravel and a little patience you can do it.