Belvidere climbs the rise west of downtown, where the streets are lined with Victorian and early-1900s houses built for merchants and mill managers rather than mill hands. Many are still single-family; others have been divided into two or three flats, and the heating equipment has followed the conversions rather than the other way round.
The houses were laid out for radiators and fireplaces, so the ductwork that serves them now was threaded through later. Long supply runs, tall windows, a big attic and a return path added years after the fact all show up in the same complaint: the front rooms heat, the back rooms do not. That is a distribution question before it is an equipment question.