i don't know what / where 'O-S-M' is, but if it's
Camino Frances and if you're starting in SJPDP, then I'd recommend the Val Carlos route to Roncesvalles, as a change, presuming you walked the Napoleon Route previously. It's lovely, walking under covered forests for the most of the day, stopping in small town ValCarlos cuts the distance in two, making Day 1 and 2 more manageable with shorter distances. It's much quieter and is a lovely way to see the mountains. Sept is a great time of year, I walked the
Camino Frances Sept2018, and bumped into local festivals in SO many towns along the way. it was always enjoyable to spend the evening and can be worth an extra day, or a scheduled rest-day. In particular in Pamplona, late September for SanFermin Txikito (their local 'little' SanFermin festival, packed full of activities, concerts, parades, etc, everything that the bigger July festival has, except the bulls) and also in Astorga in mid October ( when British, Spanish & French troops descend on the town, and Napolean and army are booed out of town !! ) These were bigger festivals but so many smaller towns had equally enjoyable fiestas. It can make finding accommodation tough somtimes, but if you look ahead at dates and plan ahead, it's worth it.