The parish priest for whom I substitute for Mass on Thursday mornings--so that he can have an overnight caring for his elderly mother--is a very gentle man, and would never presume to tell me how to celebrate Mass. He's just grateful for the regular and reliable help, and I'm happy to do it.
However, I get the feeling that Father would like me to add the Prayer to St. Michael at the end of Mass. I know that he appends his daily Masses with the prayer. He leaves a laminated copy (in English and Spanish) prominently placed on the altar.
Nevertheless, I don't do it, and nobody else in the assembly starts it spontaneously either. For one thing, I don't like adding things to the Mass, as I feel that such things detract from the 'noble simplicity' of the Roman rite. (Not that I'm not guilty of a handful of tridentine accretions in my practice of the Ordinary Form; but I'm careful only to permit myself such things at moments when nothing else is provided in the current rubrics. I feel like I'm in the spirit of the "mutual enrichment" of the two forms of the Roman rite which the Holy Father called for in his cover letter to Summorum pontificum.)
Also, because I have a psychological tendency towards a certain rigorism--I'm 'precise,' as my mother would say--I would want to pray the whole of the Leonine Prayers if I'm going to add the Prayer to St. Michael. But, as is clear, the Leonine Prayers were suppressed in 1964 by the instruction Inter oecumenici.
So, what should I do?
Continue to not add the Prayer to St. Michael, as I have been doing? Add the prayer at the end of Mass, in support of my host, and for the sake of prayerful continuity for the people? Go all the way and lead the whole of the Leonine Prayers, telling myself that the spirit of the liturgical vision of Benedict XVI trumps the prescriptions of the famous consilium for implementing Sacrosanctum Concilium?
Anybody have any other qualifications for the question? Any other documents that I don't know about?
Sancte Michael Archangele, defende nos in proelio, contra nequitiam et insidias diaboli esto praesidium. Imperet illi Deus, supplices deprecamur: tuque, Princeps militiae caelestis, Satanam aliosque spiritus malignos, qui ad perditionem animarum pervagantur in mundo, divina virtute, in infernum detrude. Amen.