You keep busy. And that's not even counting the speaker enclosures.
I only found the time for the third one. There exists a picture that aerohead posts occasionally (that I can't find via Search). His friend in the 1980s had a VW camper that he drove to Mexico one a year that had a conduit and boat wrap open-ended boat tail — a bigger cavity than the one you tested. There was some claim associated with it.