I just fitted a Webasto AirTop 3900 and it ended up going into the port lazarette with 80mm ducting to the aft cabin, salon and 60mm ducting to a closable forward cabin vent. The 90cm ducting was too big to fit. The routing was along the port side, through the hanging locker, under the sink and the galley fixtures, through the port side settee and into the port side V berth. The installer was able to use some of the existing holes moving forward and made cutouts where necessary. Given Nashira's existing equipment, the installer did not have a fun time. That said, pressing the start button beside the bed yields a toasty warmth a few minutes after startup and I'm happily confident cruising in Tassie has become a lot more comfortable in the colder months.