Adding subtitles to DVD -- how-to doesn't work

[Yes, me]

I have a ripped DVD and a subtitle file and have tried to follow the instructions here: http://ffmpegx.com/dvd_sub.html

Nothing I have tried works. Part of the problem (aside from the fact that I am a noobie) is that the How-To says: "You have an .AVI DivX, a Quicktime .MOV, a VOB or MPG movie and you want to encode it into a DVD with ffmpegX and add it selectable subtitles..."

The ripped DVD has six VOB files. Do I need to use only the first one or do I need to use all of them? When I try only the first one and select "decode with mplayer", I end up with several different files (.mpeg, .mpa, etc.) and a VIDEO_TS folder with no subtitles and a short run time. In fact, none of the files have subtitles.

I also do not understand what, in the Video window, the autosize selection does. It automatically selects "half DVD". I have changed it to "unconstrained". The resulting video seems to be correct in terms of size, but, again, there are no subtitles.

What am I doing wrong?

[Case]

If you decode with mplayer then you may use the VIDEO_TS folder itself as input.
Alternatively, you may rip as one VOB file or concatenate the VOBs of one title. See also post #1632153.

"Autosize: Use this pulldown menu to set a predefined video size values (eg VCD or SVCD), or to calculates the height from the width by applying the specified ratio (eg 2.35:1, 16:9 or 4:3). Using 16:9 ratios or presets also apply a 16:9 special flag to mpeg-2 streams."
For DVD output, you should use 'Half DVD', 'DVD' or 'DVD 16:9', as other settings may result in invalid video sizes for DVD.

[Al T]

In Filters:Subtitles I just check the VOB subtitles box, leaving everything else as it comes, and everything happens correctly. I am, however, encoding to H264 using mencoder, so this might be different to your .mpeg settings you seem to be using.