Using say PVA glue and bathroom silicone, line the sides with foam. You'd be surprised to learn that if during the next time you fly you were to remove the side panels from around the window, you'd see similar, as it attenuates noise, dampens vibration and insulates the cabin.
Our mannekin won't worry about cold, however, as he'll be flying a drophead... literally.
Top-tip: go large on applying glue to both surfaces so as to prevent wrinkles.
