I'm trying to connect our Harman XXV with Top Vent Option. Following the Harman instructions we are using seamless 6" stove pipe. We are stumped as to how to adapt the 6" outlet on the top of the unit to the 6" Heat-Fab Stove Pipe - specifically, from the 6" Top Vent to a length of Heat-Fab telescoping pipe (Selkirk #21135).

Any help would be appreciated.