Prevent subtitle stretching when viewing 16:9 letterbox?

When you view subtitles of a 16:9 project, the subtitles appear thinner when
using the letterbox-mode of a DVD player. Here is what the readme file says:

"When you view subtitles over widescreen video in 4:3 Letterbox or in 4x3
Pan & Scan mode on a set-top DVD player, the subtitles appear thinner
horizontally. This can be mitigated by increasing the horizontal scale of the
subtitle text, or by widening the subtitles's bounding box in the Monitor
panel." (http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=332138)

Is there any way to prevent the stretching (or actually not-stretching) of the
subtitles -- not just to mitigate it? I've read about dual subtitle streams and
I wonder if this is possible with Encore DVD.

Thank you,

The subtitles are generated by the DVD player during playback. Same thing for
the button subpicture highlights. The DVD spec provides more than one
"mode" for button highlights because the highlights have to line up
with the buttons. But the side effect is that you, the author, are limited in
the number of buttons that you can put on a widescreen menu. Subtitles don't
have the same "modes".