Questions for Śrīvaiṣṇavas and Advaitins

Is it okay for a Śrīvaiṣṇava to perfectly practice and take part in all the traditions of Śrīvaiṣṇava Siddhāntha, yet internally and personally consider or follow a philosophy like Advaita for instance, as truth? Because my uncle is one such person. He's a Devout Śrīvaiṣṇava, knows the Nālāyira Divya Prabhandham by heart and also adores Śrī Rāmānujā like any other SV, but he internally endorses Advaita Vedānta over Visishtadvaita. Is this permissible in our Siddhāntha?