The 200mm Polly Pipe is the way to go with a flap at One end and a handle at the other opening it via a rod/torque tube arrangement. If it is a couple of foot long you can poke it out the window far enough. Best side is with the down going propwash. Used a similar arrangement in a tiger moth before. The only messy part was getting the ashes in the pipe. I would advise to not do it in front of the family and probably not wearing black clothing. Speaking from experience.