This picture shows the only way to cool a loft area in an A frame . The top picture, forgive the shadowing, show two large 12 x 12 floor registers on the loft floor. This was the only option. Fed by two sheet metal ducts in back to back closets coming up from the furnace area. Hard pipe with a non fiberglass wrap was used to save closet space. Precision cutting saved the shelf and pole.
A Honeywell motorized damper was wired into the system so when the call for heating comes on the dampers close this way the unneeded heat goes to the lower levels. There are a few other aspects to this but we chose not sure share all our designs.