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.
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.Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster
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.Because much of what is in the published literature is nonsense,
and much of what isn’t nonsense is not in the scientific literature.
-- Sabine Hossenfelder
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