Dr. Prepare Aircon Mod

Air condition outflow mod for a Dr. Prepare portable air conditioning unit: https://www.amazon.co.uk/dp/B0CP42SSZD?psc=1&ref=ppx_yo2ov_dt_b_product_details ), I had some trouble with keeping the exhaust air from coming back into the room.The unit does come with solutions for this, but it's primarily designed with sliding windows in mind, as there is an included PVC “gasket” that fits into the gap in the opened window, and an exhaust collar (the white object in the photos) that clips into the gasket. This would work great for sliding windows, but not at all with outward opening windows. Also included is a fabric bag for non-sliding windows, which is secured by velcro with sticky tape on the back, and the exhaust pipe goes through a zipper in that bag to vent outside. This solution doesn't really work, as the mass of the exhaust pipe/collar keeps pulling the bag off the window, and the exhaust pipe alone just does not stay put in the window gap, no matter how much you deform it.S