What is the ruling on saying "Sayyiduna Abu Bakr Al-Siddiq" as opposed to "Abu Bakr Al-Siddiq" without "Sayyiduna"?

The statement by Abu Bakr, "I am a master among the masters of the Muslims," is permissible, as evidenced by 'Umar's saying, "Abu Bakr is our master, and he freed our master Bilal." This is further supported by 'Umar's words during the pledge of allegiance to Abu Bakr: "Rather, we pledge allegiance to you, for you are our master, the best among us, and the most beloved to the Messenger of Allah, peace and blessings be upon him." This is also indicated by the Prophet's saying, peace and blessings be upon him, to Sa'd ibn Mu'adh on the day of Qurayzah: "Stand up for your master," and his saying regarding Sa'd ibn 'Ubadah: "Listen to what your master says."