A lot will depend an the audience. If you are speaking (writing) to
non-dancers, surely you would refer to the Royal Scottish Dance Society,
i.e. singular. But if using RSCDS (speaking to people who know what the
acronym means), then the organisation indicates a plural. However,
"Where is the RSCDS?" would mean where are they at this time - but "Where
was the RSCDS?" meaning where were they then?
(Just throwing another spanner!)