Imperial Slug said:

I am using a portion of what I believe is a g-force script for ROTJ, but if you go to the end of my sample you can see the subtitles are too small and smack right in the center of the screen. I would like them appear as the do in the 480p conversion, but I don't know enough about Avisynth to resize them for 720p.

You just need to fiddle around with these settings:

f_wid = 9
f_pos = 465
f_siz = 36

until you're happy with the results. In your case you should increase the values. Check this out: http://avisynth.org/mediawiki/Subtitle