Well, once again I've kicked the quality of this edit up a notch.
A major bugabear for me with this edit is that the pan & scan image on the Princess and the Cobbler DVD is a really cheap transfer which goes dark on the sides - the right and bottom sides of the image in particular are much darker than the center, like a bad telecine.
Thus no matter how much time I spent placing the pan & scan image just so on the widescreen workprint and color correcting both to match exactly, the dark sides of the pan & scan insert always gave it away, and made all my best efforts look like junk.
I've solved that now.
I went into my pan & scan video files and looked for frames which were mostly just one flat color with nothing in it. I found one quickly for the main film, though for the end credits which are in widescreen, I had to hunt and create one in Photoshop from bits and pieces of frames.
Both were flat blue skies, darker on the right and bottom.
In Photoshop, I created a matte from this .... white for the light areas, black for the dark ones.
I applied this matte to the pan & scan image in Final Cut Pro. Using the matte, I lightened up the dark areas separately using color correction on a different layer, leaving the light areas unchanged.
The result? No more dark edges! The image looks like a clean transfer, transferred the same on all sides.
I replaced the files on my hard drive, and voila -- shots which looked merely good before are now seamless. Damn straight.
This has emboldened me ... I might even take on the "tree" shot in the Polo game, which I'd previously given up on as impossible to get right.