Yes Michl, long goes this thread/work, in which you show us and teach us a lot, for which we may only feel much obliged.
To lend the thread a touch of "variety", allow me post the oldest specimen kept in the Portuguese Maritime Musem, which i have twice visited and from which i keep a catalogue on the Artillery thematic.
It is known by the name of "Aljubarrota trom" although, contrary to tradition, it would have never been in this memorable battle. (quoting catalogue author Colonel Nuno Valdez dos Santos; now deceased ).
The text also says that, with its half ton weight and 1,5 mts. length, this is no more than a (loading) chamber from a huge trom or gross bombard, which possible had a 4 to 5 meters length.
Pity that when i was there i didn't take a (clandestine) picture of its touch hole. Maybe when you come down to Lisbon we go there and do it