Using AST for Captioning & Subtitles for Best Results

Has anyone used Automatic Sync Technologies for captioning and subtitles? I need captions or subtitles for .mp4 files for iPad and also for DVDs edited in FCP and authored in DVD Studio Pro. I am trying to figure out how to get the best results with the files I've received from AST. (QT.SMIL, QT.TXT & .STL). I need to do single line captions or subtitles in the upper frame of the video because the lower third has titles. When placing the .stl file in DVD Studio Pro, it looks very ratty and low-res. (I shot HD, but am outputting SD.) I also need to raise the subtitles higher so they don't block faces and am not sure how. For the MP4 files, I tried incorporating the QT.TXT file into the movie using "Add to movie" and it works fairly well, although I would like to shrink the black background box the test appears on because it is bigger than needed for one line of captions and it cuts into the video. I am new to this and AST is very DIY. Thanks for any help.