Puggo - Jar Jar's Yoda said:
neither of the DVD players that I have tried have explicit settings for 4:3 vs 16:9.

I'm surprised to read this. Of units I've seen (in passing), DVD player setup is usually accessible via the remote control's dedicated "setup" button. There may be certain models that rely on covert number-pad sequence entries or "press & hold" keys -- those would be revealed in a user's manual or a website of "tips & tricks" for DVD players (like, for example, http://www.videohelp.com).

CORRECTION: My previous mention of an "auto" option for a DVD player was (at least) inaccurate. A standard DVD player cannot determine the type of TV to which it is attached. ("Hi-Def" and up-converting players using HDMI connections may be another matter.) It requires a manual setting to indicate whether to use the anamorphic flag to "squash & bar" the picture, as needed, for a "square TV", or to ignore the anamorphic flag to allow the "wide screen TV" to "expand" the picture, as needed (if the TV's setting is to do so).