Here's what I did. I'm using the free version of DVD Rebuilder, latest versions of all the components:
Using DVD Shrink with no compression, extract just the movie to a folder on the hard disk stripping out all the alternate languages and subtitles. No need for the Huttese subtitles as we're burning them in.
In DVD-RB:
Options > AVS options > Advanced > Convert from LB 4:3 to 16:9 (applied to all titles as there's only one).
Options > AVS options > Advanced > Filter editor, copy and paste Goose's script above
Options > HC Encoder options > Best quality
Then hit "Backup DVD".
No subtitles come up. I've tried it with the font name as-is, also putting the filename of the TTF file into the subtitle() filter. What am I doing wrong?