I recently attended a Shabbat morning service in a conservative Shul. To my amazement Musaf was prayed without repetition, The Chazan started Musaf all the congregates standing and singing loud the entire Musaf Tfila with the Chazan leading. Everything seems to be according to the conservative way. (just without silent "Amida"). Acceding to the Rav he said that "we pray according to the Rambam tradition". Can you refer me to the correct source?
That is the Rambam's opinion as brought in his responsa, and the Yemanite jews who follow Rambam customs do so to this day. The bigger question is if praying with conservatives is permitted at all since they are considered Apikorsim, and they do not believe in the 13 main foundations of faith. Rabbi Ro'i Margalit