Thanks, Jeff!
Here it is.
I noticed that the encoder gave me 720 x 576 which seems wrong ( I upscaled it a long time ago) but when I tried to move it up to 1344 x 1080 the encoder wouldn’t accept it, no matter what profile and level I tried it with.

I shot this using the “Letterbox” setting on a Panasonic DVX in PAL progressive. I was later told that that’s a fake 6/19 inside a 4/3 frame, so I’m hoping the extracted image (i.e., no bars) will be an acceptable aspect ratio for YouTube.
The Sequence setting for this trial clip (shown above) is D1/ DV PAL Widescreen 16/9. The sequence setting for the entire film is D1/ DV PAL. Which should I be using?