But for future releases, how do I get the behaviour observed on retail DVDs, that is, the picture is always presented as letterboxed?
I haven't had a chance to put this to the test, but I'm going to stick my neck out and say I reckon this is something that's correctable with ifoedit.
Comparing the video attributes of your .ifo's with retail discs, the commercial discs seem to be only set for Automatic Letterboxed, whereas yours are also set to Automatic Pan&Scan. So hopefully its just a question of unchecking that Automatic Pan&Scan box.
Can anyone more knowledgeable tell me if I'm on the right track?