Hi people chaplain here. I just got finished speaking over the issue with the Rebbe. He told me I was right except for the point about davening in the shul itself. Even if not with a regular shul minyon the guests should daven the nusach of the shul. He told me a story of about a thousand viznitzer chassidim went to visit the k’vorim of tzaddikim in Europe and they were davening in the Rama’s shul. The Rebbe told everyone that they must daven ashkenaz as that is what the Ramam held.
